1 /*
  2     Copyright 2008-2025
  3         Matthias Ehmann,
  4         Michael Gerhaeuser,
  5         Carsten Miller,
  6         Bianca Valentin,
  7         Alfred Wassermann,
  8         Peter Wilfahrt
  9 
 10     This file is part of JSXGraph.
 11 
 12     JSXGraph is free software dual licensed under the GNU LGPL or MIT License.
 13 
 14     You can redistribute it and/or modify it under the terms of the
 15 
 16       * GNU Lesser General Public License as published by
 17         the Free Software Foundation, either version 3 of the License, or
 18         (at your option) any later version
 19       OR
 20       * MIT License: https://github.com/jsxgraph/jsxgraph/blob/master/LICENSE.MIT
 21 
 22     JSXGraph is distributed in the hope that it will be useful,
 23     but WITHOUT ANY WARRANTY; without even the implied warranty of
 24     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 25     GNU Lesser General Public License for more details.
 26 
 27     You should have received a copy of the GNU Lesser General Public License and
 28     the MIT License along with JSXGraph. If not, see <https://www.gnu.org/licenses/>
 29     and <https://opensource.org/licenses/MIT/>.
 30  */
 31 
 32 /*global JXG: true, define: true*/
 33 /*jslint nomen: true, plusplus: true*/
 34 
 35 /**
 36  * @fileoverview In this file the geometry element Curve is defined.
 37  */
 38 
 39 import JXG from "../jxg.js";
 40 import Clip from "../math/clip.js";
 41 import Const from "./constants.js";
 42 import Coords from "./coords.js";
 43 import Geometry from "../math/geometry.js";
 44 import GeometryElement from "./element.js";
 45 import GeonextParser from "../parser/geonext.js";
 46 import ImplicitPlot from "../math/implicitplot.js";
 47 import Mat from "../math/math.js";
 48 import Metapost from "../math/metapost.js";
 49 import Numerics from "../math/numerics.js";
 50 import Plot from "../math/plot.js";
 51 import QDT from "../math/qdt.js";
 52 import Type from "../utils/type.js";
 53 
 54 /**
 55  * Curves are the common object for function graphs, parametric curves, polar curves, and data plots.
 56  * @class Creates a new curve object. Do not use this constructor to create a curve. Use {@link JXG.Board#create} with
 57  * type {@link Curve}, or {@link Functiongraph} instead.
 58  * @augments JXG.GeometryElement
 59  * @param {String|JXG.Board} board The board the new curve is drawn on.
 60  * @param {Array} parents defining terms An array with the function terms or the data points of the curve.
 61  * @param {Object} attributes Defines the visual appearance of the curve.
 62  * @see JXG.Board#generateName
 63  * @see JXG.Board#addCurve
 64  */
 65 JXG.Curve = function (board, parents, attributes) {
 66     this.constructor(board, attributes, Const.OBJECT_TYPE_CURVE, Const.OBJECT_CLASS_CURVE);
 67 
 68     this.points = [];
 69     /**
 70      * Number of points on curves. This value changes
 71      * between numberPointsLow and numberPointsHigh.
 72      * It is set in {@link JXG.Curve#updateCurve}.
 73      */
 74     this.numberPoints = this.evalVisProp('numberpointshigh');
 75 
 76     this.bezierDegree = 1;
 77 
 78     /**
 79      * Array holding the x-coordinates of a data plot.
 80      * This array can be updated during run time by overwriting
 81      * the method {@link JXG.Curve#updateDataArray}.
 82      * @type array
 83      */
 84     this.dataX = null;
 85 
 86     /**
 87      * Array holding the y-coordinates of a data plot.
 88      * This array can be updated during run time by overwriting
 89      * the method {@link JXG.Curve#updateDataArray}.
 90      * @type array
 91      */
 92     this.dataY = null;
 93 
 94     /**
 95      * Array of ticks storing all the ticks on this curve. Do not set this field directly and use
 96      * {@link JXG.Curve#addTicks} and {@link JXG.Curve#removeTicks} to add and remove ticks to and
 97      * from the curve.
 98      * @type Array
 99      * @see JXG.Ticks
100      */
101     this.ticks = [];
102 
103     /**
104      * Stores a quadtree if it is required. The quadtree is generated in the curve
105      * updates and can be used to speed up the hasPoint method.
106      * @type JXG.Math.Quadtree
107      */
108     this.qdt = null;
109 
110     if (Type.exists(parents[0])) {
111         this.varname = parents[0];
112     } else {
113         this.varname = "x";
114     }
115 
116     // function graphs: "x"
117     this.xterm = parents[1];
118     // function graphs: e.g. "x^2"
119     this.yterm = parents[2];
120 
121     // Converts GEONExT syntax into JavaScript syntax
122     this.generateTerm(this.varname, this.xterm, this.yterm, parents[3], parents[4]);
123     // First evaluation of the curve
124     this.updateCurve();
125 
126     this.id = this.board.setId(this, "G");
127     this.board.renderer.drawCurve(this);
128 
129     this.board.finalizeAdding(this);
130 
131     this.createGradient();
132     this.elType = "curve";
133     this.createLabel();
134 
135     if (Type.isString(this.xterm)) {
136         this.notifyParents(this.xterm);
137     }
138     if (Type.isString(this.yterm)) {
139         this.notifyParents(this.yterm);
140     }
141 
142     this.methodMap = Type.deepCopy(this.methodMap, {
143         generateTerm: "generateTerm",
144         setTerm: "generateTerm",
145         move: "moveTo",
146         moveTo: "moveTo",
147         MinX: "minX",
148         MaxX: "maxX"
149     });
150 };
151 
152 JXG.Curve.prototype = new GeometryElement();
153 
154 JXG.extend(
155     JXG.Curve.prototype,
156     /** @lends JXG.Curve.prototype */ {
157         /**
158          * Gives the default value of the left bound for the curve.
159          * May be overwritten in {@link JXG.Curve#generateTerm}.
160          * @returns {Number} Left bound for the curve.
161          */
162         minX: function () {
163             var leftCoords;
164 
165             if (this.evalVisProp('curvetype') === "polar") {
166                 return 0;
167             }
168 
169             leftCoords = new Coords(
170                 Const.COORDS_BY_SCREEN,
171                 [-this.board.canvasWidth * 0.1, 0],
172                 this.board,
173                 false
174             );
175             return leftCoords.usrCoords[1];
176         },
177 
178         /**
179          * Gives the default value of the right bound for the curve.
180          * May be overwritten in {@link JXG.Curve#generateTerm}.
181          * @returns {Number} Right bound for the curve.
182          */
183         maxX: function () {
184             var rightCoords;
185 
186             if (this.evalVisProp('curvetype') === "polar") {
187                 return 2 * Math.PI;
188             }
189             rightCoords = new Coords(
190                 Const.COORDS_BY_SCREEN,
191                 [this.board.canvasWidth * 1.1, 0],
192                 this.board,
193                 false
194             );
195 
196             return rightCoords.usrCoords[1];
197         },
198 
199         /**
200          * The parametric function which defines the x-coordinate of the curve.
201          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
202          * @param {Boolean} suspendUpdate A boolean flag which is false for the
203          * first call of the function during a fresh plot of the curve and true
204          * for all subsequent calls of the function. This may be used to speed up the
205          * plotting of the curve, if the e.g. the curve depends on some input elements.
206          * @returns {Number} x-coordinate of the curve at t.
207          */
208         X: function (t) {
209             return NaN;
210         },
211 
212         /**
213          * The parametric function which defines the y-coordinate of the curve.
214          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
215          * @param {Boolean} suspendUpdate A boolean flag which is false for the
216          * first call of the function during a fresh plot of the curve and true
217          * for all subsequent calls of the function. This may be used to speed up the
218          * plotting of the curve, if the e.g. the curve depends on some input elements.
219          * @returns {Number} y-coordinate of the curve at t.
220          */
221         Y: function (t) {
222             return NaN;
223         },
224 
225         /**
226          * Treat the curve as curve with homogeneous coordinates.
227          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
228          * @returns {Number} Always 1.0
229          */
230         Z: function (t) {
231             return 1;
232         },
233 
234         /**
235          * Checks whether (x,y) is near the curve.
236          * @param {Number} x Coordinate in x direction, screen coordinates.
237          * @param {Number} y Coordinate in y direction, screen coordinates.
238          * @param {Number} start Optional start index for search on data plots.
239          * @returns {Boolean} True if (x,y) is near the curve, False otherwise.
240          */
241         hasPoint: function (x, y, start) {
242             var t, c, i, tX, tY,
243                 checkPoint, len, invMat, isIn,
244                 res = [],
245                 points,
246                 qdt,
247                 steps = this.evalVisProp('numberpointslow'),
248                 d = (this.maxX() - this.minX()) / steps,
249                 prec, type,
250                 dist = Infinity,
251                 ux2, uy2,
252                 ev_ct,
253                 mi, ma,
254                 suspendUpdate = true;
255 
256             if (Type.isObject(this.evalVisProp('precision'))) {
257                 type = this.board._inputDevice;
258                 prec = this.evalVisProp('precision.' + type);
259             } else {
260                 // 'inherit'
261                 prec = this.board.options.precision.hasPoint;
262             }
263 
264             // From now on, x,y are usrCoords
265             checkPoint = new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board, false);
266             x = checkPoint.usrCoords[1];
267             y = checkPoint.usrCoords[2];
268 
269             // Handle inner points of the curve
270             if (this.bezierDegree === 1 && this.evalVisProp('hasinnerpoints')) {
271                 isIn = Geometry.windingNumber([1, x, y], this.points, true);
272                 if (isIn !== 0) {
273                     return true;
274                 }
275             }
276 
277             // We use usrCoords. Only in the final distance calculation
278             // screen coords are used
279             prec += this.evalVisProp('strokewidth') * 0.5;
280             prec *= prec; // We do not want to take sqrt
281             ux2 = this.board.unitX * this.board.unitX;
282             uy2 = this.board.unitY * this.board.unitY;
283 
284             mi = this.minX();
285             ma = this.maxX();
286             if (Type.exists(this._visibleArea)) {
287                 mi = this._visibleArea[0];
288                 ma = this._visibleArea[1];
289                 d = (ma - mi) / steps;
290             }
291 
292             ev_ct = this.evalVisProp('curvetype');
293             if (ev_ct === "parameter" || ev_ct === "polar") {
294                 // Transform the mouse/touch coordinates
295                 // back to the original position of the curve.
296                 // This is needed, because we work with the function terms, not the points.
297                 if (this.transformations.length > 0) {
298                     this.updateTransformMatrix();
299                     invMat = Mat.inverse(this.transformMat);
300                     c = Mat.matVecMult(invMat, [1, x, y]);
301                     x = c[1];
302                     y = c[2];
303                 }
304 
305                 // Brute force search for a point on the curve close to the mouse pointer
306                 for (i = 0, t = mi; i < steps; i++) {
307                     tX = this.X(t, suspendUpdate);
308                     tY = this.Y(t, suspendUpdate);
309 
310                     dist = (x - tX) * (x - tX) * ux2 + (y - tY) * (y - tY) * uy2;
311 
312                     if (dist <= prec) {
313                         return true;
314                     }
315 
316                     t += d;
317                 }
318             } else if (ev_ct === "plot" || ev_ct === "functiongraph") {
319                 // Here, we can ignore transformations of the curve,
320                 // since we are working directly with the points.
321 
322                 if (!Type.exists(start) || start < 0) {
323                     start = 0;
324                 }
325 
326                 if (
327                     Type.exists(this.qdt) &&
328                     this.evalVisProp('useqdt') &&
329                     this.bezierDegree !== 3
330                 ) {
331                     qdt = this.qdt.query(new Coords(Const.COORDS_BY_USER, [x, y], this.board));
332                     points = qdt.points;
333                     len = points.length;
334                 } else {
335                     points = this.points;
336                     len = this.numberPoints - 1;
337                 }
338 
339                 for (i = start; i < len; i++) {
340                     if (this.bezierDegree === 3) {
341                         //res.push(Geometry.projectCoordsToBeziersegment([1, x, y], this, i));
342                         res = Geometry.projectCoordsToBeziersegment([1, x, y], this, i);
343                     } else {
344                         if (qdt) {
345                             if (points[i].prev) {
346                                 res = Geometry.projectCoordsToSegment(
347                                     [1, x, y],
348                                     points[i].prev.usrCoords,
349                                     points[i].usrCoords
350                                 );
351                             }
352 
353                             // If the next point in the array is the same as the current points
354                             // next neighbor we don't have to project it onto that segment because
355                             // that will already be done in the next iteration of this loop.
356                             if (points[i].next && points[i + 1] !== points[i].next) {
357                                 res = Geometry.projectCoordsToSegment(
358                                     [1, x, y],
359                                     points[i].usrCoords,
360                                     points[i].next.usrCoords
361                                 );
362                             }
363                         } else {
364                             res = Geometry.projectCoordsToSegment(
365                                 [1, x, y],
366                                 points[i].usrCoords,
367                                 points[i + 1].usrCoords
368                             );
369                         }
370                     }
371 
372                     if (
373                         res[1] >= 0 &&
374                         res[1] <= 1 &&
375                         (x - res[0][1]) * (x - res[0][1]) * ux2 +
376                         (y - res[0][2]) * (y - res[0][2]) * uy2 <=
377                         prec
378                     ) {
379                         return true;
380                     }
381                 }
382                 return false;
383             }
384             return dist < prec;
385         },
386 
387         /**
388          * Allocate points in the Coords array this.points
389          */
390         allocatePoints: function () {
391             var i, len;
392 
393             len = this.numberPoints;
394 
395             if (this.points.length < this.numberPoints) {
396                 for (i = this.points.length; i < len; i++) {
397                     this.points[i] = new Coords(
398                         Const.COORDS_BY_USER,
399                         [0, 0],
400                         this.board,
401                         false
402                     );
403                 }
404             }
405         },
406 
407         /**
408          * Computes for equidistant points on the x-axis the values of the function
409          * @returns {JXG.Curve} Reference to the curve object.
410          * @see JXG.Curve#updateCurve
411          */
412         update: function () {
413             if (this.needsUpdate) {
414                 if (this.evalVisProp('trace')) {
415                     this.cloneToBackground(true);
416                 }
417                 this.updateCurve();
418             }
419 
420             return this;
421         },
422 
423         /**
424          * Updates the visual contents of the curve.
425          * @returns {JXG.Curve} Reference to the curve object.
426          */
427         updateRenderer: function () {
428             //var wasReal;
429 
430             if (!this.needsUpdate) {
431                 return this;
432             }
433 
434             if (this.visPropCalc.visible) {
435                 // wasReal = this.isReal;
436 
437                 this.isReal = Plot.checkReal(this.points);
438 
439                 if (
440                     //wasReal &&
441                     !this.isReal
442                 ) {
443                     this.updateVisibility(false);
444                 }
445             }
446 
447             if (this.visPropCalc.visible) {
448                 this.board.renderer.updateCurve(this);
449             }
450 
451             /* Update the label if visible. */
452             if (
453                 this.hasLabel &&
454                 this.visPropCalc.visible &&
455                 this.label &&
456                 this.label.visPropCalc.visible &&
457                 this.isReal
458             ) {
459                 this.label.update();
460                 this.board.renderer.updateText(this.label);
461             }
462 
463             // Update rendNode display
464             this.setDisplayRendNode();
465             // if (this.visPropCalc.visible !== this.visPropOld.visible) {
466             //     this.board.renderer.display(this, this.visPropCalc.visible);
467             //     this.visPropOld.visible = this.visPropCalc.visible;
468             //
469             //     if (this.hasLabel) {
470             //         this.board.renderer.display(this.label, this.label.visPropCalc.visible);
471             //     }
472             // }
473 
474             this.needsUpdate = false;
475             return this;
476         },
477 
478         /**
479          * For dynamic dataplots updateCurve can be used to compute new entries
480          * for the arrays {@link JXG.Curve#dataX} and {@link JXG.Curve#dataY}. It
481          * is used in {@link JXG.Curve#updateCurve}. Default is an empty method, can
482          * be overwritten by the user.
483          *
484          *
485          * @example
486          * // This example overwrites the updateDataArray method.
487          * // There, new values for the arrays JXG.Curve.dataX and JXG.Curve.dataY
488          * // are computed from the value of the slider N
489          *
490          * var N = board.create('slider', [[0,1.5],[3,1.5],[1,3,40]], {name:'n',snapWidth:1});
491          * var circ = board.create('circle',[[4,-1.5],1],{strokeWidth:1, strokecolor:'black', strokeWidth:2,
492          * 		fillColor:'#0055ff13'});
493          *
494          * var c = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:2});
495          * c.updateDataArray = function() {
496          *         var r = 1, n = Math.floor(N.Value()),
497          *             x = [0], y = [0],
498          *             phi = Math.PI/n,
499          *             h = r*Math.cos(phi),
500          *             s = r*Math.sin(phi),
501          *             i, j,
502          *             px = 0, py = 0, sgn = 1,
503          *             d = 16,
504          *             dt = phi/d,
505          *             pt;
506          *
507          *         for (i = 0; i < n; i++) {
508          *             for (j = -d; j <= d; j++) {
509          *                 pt = dt*j;
510          *                 x.push(px + r*Math.sin(pt));
511          *                 y.push(sgn*r*Math.cos(pt) - (sgn-1)*h*0.5);
512          *             }
513          *             px += s;
514          *             sgn *= (-1);
515          *         }
516          *         x.push((n - 1)*s);
517          *         y.push(h + (sgn - 1)*h*0.5);
518          *         this.dataX = x;
519          *         this.dataY = y;
520          *     }
521          *
522          * var c2 = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:1});
523          * c2.updateDataArray = function() {
524          *         var r = 1, n = Math.floor(N.Value()),
525          *             px = circ.midpoint.X(), py = circ.midpoint.Y(),
526          *             x = [px], y = [py],
527          *             phi = Math.PI/n,
528          *             s = r*Math.sin(phi),
529          *             i, j,
530          *             d = 16,
531          *             dt = phi/d,
532          *             pt = Math.PI*0.5+phi;
533          *
534          *         for (i = 0; i < n; i++) {
535          *             for (j= -d; j <= d; j++) {
536          *                 x.push(px + r*Math.cos(pt));
537          *                 y.push(py + r*Math.sin(pt));
538          *                 pt -= dt;
539          *             }
540          *             x.push(px);
541          *             y.push(py);
542          *             pt += dt;
543          *         }
544          *         this.dataX = x;
545          *         this.dataY = y;
546          *     }
547          *     board.update();
548          *
549          * </pre><div id="JXG20bc7802-e69e-11e5-b1bf-901b0e1b8723" class="jxgbox" style="width: 600px; height: 400px;"></div>
550          * <script type="text/javascript">
551          *     (function() {
552          *         var board = JXG.JSXGraph.initBoard('JXG20bc7802-e69e-11e5-b1bf-901b0e1b8723',
553          *             {boundingbox: [-1.5,2,8,-3], keepaspectratio: true, axis: true, showcopyright: false, shownavigation: false});
554          *             var N = board.create('slider', [[0,1.5],[3,1.5],[1,3,40]], {name:'n',snapWidth:1});
555          *             var circ = board.create('circle',[[4,-1.5],1],{strokeWidth:1, strokecolor:'black',
556          *             strokeWidth:2, fillColor:'#0055ff13'});
557          *
558          *             var c = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:2});
559          *             c.updateDataArray = function() {
560          *                     var r = 1, n = Math.floor(N.Value()),
561          *                         x = [0], y = [0],
562          *                         phi = Math.PI/n,
563          *                         h = r*Math.cos(phi),
564          *                         s = r*Math.sin(phi),
565          *                         i, j,
566          *                         px = 0, py = 0, sgn = 1,
567          *                         d = 16,
568          *                         dt = phi/d,
569          *                         pt;
570          *
571          *                     for (i=0;i<n;i++) {
572          *                         for (j=-d;j<=d;j++) {
573          *                             pt = dt*j;
574          *                             x.push(px+r*Math.sin(pt));
575          *                             y.push(sgn*r*Math.cos(pt)-(sgn-1)*h*0.5);
576          *                         }
577          *                         px += s;
578          *                         sgn *= (-1);
579          *                     }
580          *                     x.push((n-1)*s);
581          *                     y.push(h+(sgn-1)*h*0.5);
582          *                     this.dataX = x;
583          *                     this.dataY = y;
584          *                 }
585          *
586          *             var c2 = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:1});
587          *             c2.updateDataArray = function() {
588          *                     var r = 1, n = Math.floor(N.Value()),
589          *                         px = circ.midpoint.X(), py = circ.midpoint.Y(),
590          *                         x = [px], y = [py],
591          *                         phi = Math.PI/n,
592          *                         s = r*Math.sin(phi),
593          *                         i, j,
594          *                         d = 16,
595          *                         dt = phi/d,
596          *                         pt = Math.PI*0.5+phi;
597          *
598          *                     for (i=0;i<n;i++) {
599          *                         for (j=-d;j<=d;j++) {
600          *                             x.push(px+r*Math.cos(pt));
601          *                             y.push(py+r*Math.sin(pt));
602          *                             pt -= dt;
603          *                         }
604          *                         x.push(px);
605          *                         y.push(py);
606          *                         pt += dt;
607          *                     }
608          *                     this.dataX = x;
609          *                     this.dataY = y;
610          *                 }
611          *                 board.update();
612          *
613          *     })();
614          *
615          * </script><pre>
616          *
617          * @example
618          * // This is an example which overwrites updateDataArray and produces
619          * // a Bezier curve of degree three.
620          * var A = board.create('point', [-3,3]);
621          * var B = board.create('point', [3,-2]);
622          * var line = board.create('segment', [A,B]);
623          *
624          * var height = 0.5; // height of the curly brace
625          *
626          * // Curly brace
627          * var crl = board.create('curve', [[0],[0]], {strokeWidth:1, strokeColor:'black'});
628          * crl.bezierDegree = 3;
629          * crl.updateDataArray = function() {
630          *     var d = [B.X()-A.X(), B.Y()-A.Y()],
631          *         dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
632          *         mid = [(A.X()+B.X())*0.5, (A.Y()+B.Y())*0.5];
633          *
634          *     d[0] *= height/dl;
635          *     d[1] *= height/dl;
636          *
637          *     this.dataX = [ A.X(), A.X()-d[1], mid[0], mid[0]-d[1], mid[0], B.X()-d[1], B.X() ];
638          *     this.dataY = [ A.Y(), A.Y()+d[0], mid[1], mid[1]+d[0], mid[1], B.Y()+d[0], B.Y() ];
639          * };
640          *
641          * // Text
642          * var txt = board.create('text', [
643          *                     function() {
644          *                         var d = [B.X()-A.X(), B.Y()-A.Y()],
645          *                             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
646          *                             mid = (A.X()+B.X())*0.5;
647          *
648          *                         d[1] *= height/dl;
649          *                         return mid-d[1]+0.1;
650          *                     },
651          *                     function() {
652          *                         var d = [B.X()-A.X(), B.Y()-A.Y()],
653          *                             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
654          *                             mid = (A.Y()+B.Y())*0.5;
655          *
656          *                         d[0] *= height/dl;
657          *                         return mid+d[0]+0.1;
658          *                     },
659          *                     function() { return "length=" + JXG.toFixed(B.Dist(A), 2); }
660          *                 ]);
661          *
662          *
663          * board.update(); // This update is necessary to call updateDataArray the first time.
664          *
665          * </pre><div id="JXGa61a4d66-e69f-11e5-b1bf-901b0e1b8723"  class="jxgbox" style="width: 300px; height: 300px;"></div>
666          * <script type="text/javascript">
667          *     (function() {
668          *      var board = JXG.JSXGraph.initBoard('JXGa61a4d66-e69f-11e5-b1bf-901b0e1b8723',
669          *             {boundingbox: [-4, 4, 4,-4], axis: true, showcopyright: false, shownavigation: false});
670          *     var A = board.create('point', [-3,3]);
671          *     var B = board.create('point', [3,-2]);
672          *     var line = board.create('segment', [A,B]);
673          *
674          *     var height = 0.5; // height of the curly brace
675          *
676          *     // Curly brace
677          *     var crl = board.create('curve', [[0],[0]], {strokeWidth:1, strokeColor:'black'});
678          *     crl.bezierDegree = 3;
679          *     crl.updateDataArray = function() {
680          *         var d = [B.X()-A.X(), B.Y()-A.Y()],
681          *             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
682          *             mid = [(A.X()+B.X())*0.5, (A.Y()+B.Y())*0.5];
683          *
684          *         d[0] *= height/dl;
685          *         d[1] *= height/dl;
686          *
687          *         this.dataX = [ A.X(), A.X()-d[1], mid[0], mid[0]-d[1], mid[0], B.X()-d[1], B.X() ];
688          *         this.dataY = [ A.Y(), A.Y()+d[0], mid[1], mid[1]+d[0], mid[1], B.Y()+d[0], B.Y() ];
689          *     };
690          *
691          *     // Text
692          *     var txt = board.create('text', [
693          *                         function() {
694          *                             var d = [B.X()-A.X(), B.Y()-A.Y()],
695          *                                 dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
696          *                                 mid = (A.X()+B.X())*0.5;
697          *
698          *                             d[1] *= height/dl;
699          *                             return mid-d[1]+0.1;
700          *                         },
701          *                         function() {
702          *                             var d = [B.X()-A.X(), B.Y()-A.Y()],
703          *                                 dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
704          *                                 mid = (A.Y()+B.Y())*0.5;
705          *
706          *                             d[0] *= height/dl;
707          *                             return mid+d[0]+0.1;
708          *                         },
709          *                         function() { return "length="+JXG.toFixed(B.Dist(A), 2); }
710          *                     ]);
711          *
712          *
713          *     board.update(); // This update is necessary to call updateDataArray the first time.
714          *
715          *     })();
716          *
717          * </script><pre>
718          *
719          *
720          */
721         updateDataArray: function () {
722             // this used to return this, but we shouldn't rely on the user to implement it.
723         },
724 
725         /**
726          * Computes the curve path
727          * @see JXG.Curve#update
728          * @returns {JXG.Curve} Reference to the curve object.
729          */
730         updateCurve: function () {
731             var i, len, mi, ma,
732                 x, y,
733                 version = this.visProp.plotversion,
734                 //t1, t2, l1,
735                 suspendUpdate = false;
736 
737             this.updateTransformMatrix();
738             this.updateDataArray();
739             mi = this.minX();
740             ma = this.maxX();
741 
742             // Discrete data points
743             // x-coordinates are in an array
744             if (Type.exists(this.dataX)) {
745                 this.numberPoints = this.dataX.length;
746                 len = this.numberPoints;
747 
748                 // It is possible, that the array length has increased.
749                 this.allocatePoints();
750 
751                 for (i = 0; i < len; i++) {
752                     x = i;
753 
754                     // y-coordinates are in an array
755                     if (Type.exists(this.dataY)) {
756                         y = i;
757                         // The last parameter prevents rounding in usr2screen().
758                         this.points[i].setCoordinates(
759                             Const.COORDS_BY_USER,
760                             [this.dataX[i], this.dataY[i]],
761                             false
762                         );
763                     } else {
764                         // discrete x data, continuous y data
765                         y = this.X(x);
766                         // The last parameter prevents rounding in usr2screen().
767                         this.points[i].setCoordinates(
768                             Const.COORDS_BY_USER,
769                             [this.dataX[i], this.Y(y, suspendUpdate)],
770                             false
771                         );
772                     }
773                     this.points[i]._t = i;
774 
775                     // this.updateTransform(this.points[i]);
776                     suspendUpdate = true;
777                 }
778                 // continuous x data
779             } else {
780                 if (this.evalVisProp('doadvancedplot')) {
781                     // console.time("plot");
782 
783                     if (version === 1 || this.evalVisProp('doadvancedplotold')) {
784                         Plot.updateParametricCurveOld(this, mi, ma);
785                     } else if (version === 2) {
786                         Plot.updateParametricCurve_v2(this, mi, ma);
787                     } else if (version === 3) {
788                         Plot.updateParametricCurve_v3(this, mi, ma);
789                     } else if (version === 4) {
790                         Plot.updateParametricCurve_v4(this, mi, ma);
791                     } else {
792                         Plot.updateParametricCurve_v2(this, mi, ma);
793                     }
794                     // console.timeEnd("plot");
795                 } else {
796                     if (this.board.updateQuality === this.board.BOARD_QUALITY_HIGH) {
797                         this.numberPoints = this.evalVisProp('numberpointshigh');
798                     } else {
799                         this.numberPoints = this.evalVisProp('numberpointslow');
800                     }
801 
802                     // It is possible, that the array length has increased.
803                     this.allocatePoints();
804                     Plot.updateParametricCurveNaive(this, mi, ma, this.numberPoints);
805                 }
806                 len = this.numberPoints;
807 
808                 if (
809                     this.evalVisProp('useqdt') &&
810                     this.board.updateQuality === this.board.BOARD_QUALITY_HIGH
811                 ) {
812                     this.qdt = new QDT(this.board.getBoundingBox());
813                     for (i = 0; i < this.points.length; i++) {
814                         this.qdt.insert(this.points[i]);
815 
816                         if (i > 0) {
817                             this.points[i].prev = this.points[i - 1];
818                         }
819 
820                         if (i < len - 1) {
821                             this.points[i].next = this.points[i + 1];
822                         }
823                     }
824                 }
825 
826                 // for (i = 0; i < len; i++) {
827                 //     this.updateTransform(this.points[i]);
828                 // }
829             }
830 
831             if (
832                 this.evalVisProp('curvetype') !== "plot" &&
833                 this.evalVisProp('rdpsmoothing')
834             ) {
835                 // console.time("rdp");
836                 this.points = Numerics.RamerDouglasPeucker(this.points, 0.2);
837                 this.numberPoints = this.points.length;
838                 // console.timeEnd("rdp");
839                 // console.log(this.numberPoints);
840             }
841 
842             len = this.numberPoints;
843             for (i = 0; i < len; i++) {
844                 this.updateTransform(this.points[i]);
845             }
846 
847             return this;
848         },
849 
850         updateTransformMatrix: function () {
851             var t,
852                 i,
853                 len = this.transformations.length;
854 
855             this.transformMat = [
856                 [1, 0, 0],
857                 [0, 1, 0],
858                 [0, 0, 1]
859             ];
860 
861             for (i = 0; i < len; i++) {
862                 t = this.transformations[i];
863                 t.update();
864                 this.transformMat = Mat.matMatMult(t.matrix, this.transformMat);
865             }
866 
867             return this;
868         },
869 
870         /**
871          * Applies the transformations of the curve to the given point <tt>p</tt>.
872          * Before using it, {@link JXG.Curve#updateTransformMatrix} has to be called.
873          * @param {JXG.Point} p
874          * @returns {JXG.Point} The given point.
875          */
876         updateTransform: function (p) {
877             var c,
878                 len = this.transformations.length;
879 
880             if (len > 0) {
881                 c = Mat.matVecMult(this.transformMat, p.usrCoords);
882                 p.setCoordinates(Const.COORDS_BY_USER, c, false, true);
883             }
884 
885             return p;
886         },
887 
888         /**
889          * Add transformations to this curve.
890          * @param {JXG.Transformation|Array} transform Either one {@link JXG.Transformation} or an array of {@link JXG.Transformation}s.
891          * @returns {JXG.Curve} Reference to the curve object.
892          */
893         addTransform: function (transform) {
894             var i,
895                 list = Type.isArray(transform) ? transform : [transform],
896                 len = list.length;
897 
898             for (i = 0; i < len; i++) {
899                 this.transformations.push(list[i]);
900             }
901 
902             return this;
903         },
904 
905         /**
906          * Generate the method curve.X() in case curve.dataX is an array
907          * and generate the method curve.Y() in case curve.dataY is an array.
908          * @private
909          * @param {String} which Either 'X' or 'Y'
910          * @returns {function}
911          **/
912         interpolationFunctionFromArray: function (which) {
913             var data = "data" + which,
914                 that = this;
915 
916             return function (t, suspendedUpdate) {
917                 var i,
918                     j,
919                     t0,
920                     t1,
921                     arr = that[data],
922                     len = arr.length,
923                     last,
924                     f = [];
925 
926                 if (isNaN(t)) {
927                     return NaN;
928                 }
929 
930                 if (t < 0) {
931                     if (Type.isFunction(arr[0])) {
932                         return arr[0]();
933                     }
934 
935                     return arr[0];
936                 }
937 
938                 if (that.bezierDegree === 3) {
939                     last = (len - 1) / 3;
940 
941                     if (t >= last) {
942                         if (Type.isFunction(arr[arr.length - 1])) {
943                             return arr[arr.length - 1]();
944                         }
945 
946                         return arr[arr.length - 1];
947                     }
948 
949                     i = Math.floor(t) * 3;
950                     t0 = t % 1;
951                     t1 = 1 - t0;
952 
953                     for (j = 0; j < 4; j++) {
954                         if (Type.isFunction(arr[i + j])) {
955                             f[j] = arr[i + j]();
956                         } else {
957                             f[j] = arr[i + j];
958                         }
959                     }
960 
961                     return (
962                         t1 * t1 * (t1 * f[0] + 3 * t0 * f[1]) +
963                         (3 * t1 * f[2] + t0 * f[3]) * t0 * t0
964                     );
965                 }
966 
967                 if (t > len - 2) {
968                     i = len - 2;
969                 } else {
970                     i = parseInt(Math.floor(t), 10);
971                 }
972 
973                 if (i === t) {
974                     if (Type.isFunction(arr[i])) {
975                         return arr[i]();
976                     }
977                     return arr[i];
978                 }
979 
980                 for (j = 0; j < 2; j++) {
981                     if (Type.isFunction(arr[i + j])) {
982                         f[j] = arr[i + j]();
983                     } else {
984                         f[j] = arr[i + j];
985                     }
986                 }
987                 return f[0] + (f[1] - f[0]) * (t - i);
988             };
989         },
990 
991         /**
992          * Converts the JavaScript/JessieCode/GEONExT syntax of the defining function term into JavaScript.
993          * New methods X() and Y() for the Curve object are generated, further
994          * new methods for minX() and maxX().
995          * If mi or ma are not supplied, default functions are set.
996          *
997          * @param {String} varname Name of the parameter in xterm and yterm, e.g. 'x' or 't'
998          * @param {String|Number|Function|Array} xterm Term for the x coordinate. Can also be an array consisting of discrete values.
999          * @param {String|Number|Function|Array} yterm Term for the y coordinate. Can also be an array consisting of discrete values.
1000          * @param {String|Number|Function} [mi] Lower bound on the parameter
1001          * @param {String|Number|Function} [ma] Upper bound on the parameter
1002          * @see JXG.GeonextParser.geonext2JS
1003          */
1004         generateTerm: function (varname, xterm, yterm, mi, ma) {
1005             var fx, fy, mat;
1006 
1007             // Generate the methods X() and Y()
1008             if (Type.isArray(xterm)) {
1009                 // Discrete data
1010                 this.dataX = xterm;
1011 
1012                 this.numberPoints = this.dataX.length;
1013                 this.X = this.interpolationFunctionFromArray.apply(this, ["X"]);
1014                 this.visProp.curvetype = "plot";
1015                 this.isDraggable = true;
1016             } else {
1017                 // Continuous data
1018                 this.X = Type.createFunction(xterm, this.board, varname);
1019                 if (Type.isString(xterm)) {
1020                     this.visProp.curvetype = "functiongraph";
1021                 } else if (Type.isFunction(xterm) || Type.isNumber(xterm)) {
1022                     this.visProp.curvetype = "parameter";
1023                 }
1024 
1025                 this.isDraggable = true;
1026             }
1027 
1028             if (Type.isArray(yterm)) {
1029                 this.dataY = yterm;
1030                 this.Y = this.interpolationFunctionFromArray.apply(this, ["Y"]);
1031             } else if (!Type.exists(yterm)) {
1032                 // Discrete data as an array of coordinate pairs,
1033                 // i.e. transposed input
1034                 mat = Mat.transpose(xterm);
1035                 this.dataX = mat[0];
1036                 this.dataY = mat[1];
1037                 this.numberPoints = this.dataX.length;
1038                 this.Y = this.interpolationFunctionFromArray.apply(this, ["Y"]);
1039             } else {
1040                 this.Y = Type.createFunction(yterm, this.board, varname);
1041             }
1042 
1043             /**
1044              * Polar form
1045              * Input data is function xterm() and offset coordinates yterm
1046              */
1047             if (Type.isFunction(xterm) && Type.isArray(yterm)) {
1048                 // Xoffset, Yoffset
1049                 fx = Type.createFunction(yterm[0], this.board, "");
1050                 fy = Type.createFunction(yterm[1], this.board, "");
1051 
1052                 this.X = function (phi) {
1053                     return xterm(phi) * Math.cos(phi) + fx();
1054                 };
1055                 this.X.deps = fx.deps;
1056 
1057                 this.Y = function (phi) {
1058                     return xterm(phi) * Math.sin(phi) + fy();
1059                 };
1060                 this.Y.deps = fy.deps;
1061 
1062                 this.visProp.curvetype = "polar";
1063             }
1064 
1065             // Set the upper and lower bounds for the parameter of the curve.
1066             // If not defined, reset the bounds to the default values
1067             // given in Curve.prototype.minX, Curve.prototype.maxX
1068             if (Type.exists(mi)) {
1069                 this.minX = Type.createFunction(mi, this.board, "");
1070             } else {
1071                 delete this.minX;
1072             }
1073             if (Type.exists(ma)) {
1074                 this.maxX = Type.createFunction(ma, this.board, "");
1075             } else {
1076                 delete this.maxX;
1077             }
1078 
1079             this.addParentsFromJCFunctions([this.X, this.Y, this.minX, this.maxX]);
1080         },
1081 
1082         /**
1083          * Finds dependencies in a given term and notifies the parents by adding the
1084          * dependent object to the found objects child elements.
1085          * @param {String} contentStr String containing dependencies for the given object.
1086          */
1087         notifyParents: function (contentStr) {
1088             var fstr,
1089                 dep,
1090                 isJessieCode = false,
1091                 obj;
1092 
1093             // Read dependencies found by the JessieCode parser
1094             obj = { xterm: 1, yterm: 1 };
1095             for (fstr in obj) {
1096                 if (
1097                     obj.hasOwnProperty(fstr) &&
1098                     this.hasOwnProperty(fstr) &&
1099                     this[fstr].origin
1100                 ) {
1101                     isJessieCode = true;
1102                     for (dep in this[fstr].origin.deps) {
1103                         if (this[fstr].origin.deps.hasOwnProperty(dep)) {
1104                             this[fstr].origin.deps[dep].addChild(this);
1105                         }
1106                     }
1107                 }
1108             }
1109 
1110             if (!isJessieCode) {
1111                 GeonextParser.findDependencies(this, contentStr, this.board);
1112             }
1113         },
1114 
1115         /**
1116          * Position a curve label according to the attributes "position" and distance.
1117          * This function is also used for angle, arc and sector.
1118          *
1119          * @param {String} pos
1120          * @param {Number} distance
1121          * @returns {JXG.Coords}
1122          */
1123         getLabelPosition: function(pos, distance) {
1124             var x, y, xy,
1125                 c, d, e,
1126                 lbda,
1127                 t, dx, dy,
1128                 dist = 1.5;
1129 
1130             xy = Type.parsePosition(pos);
1131             lbda = Type.parseNumber(xy.pos, this.maxX() - this.minX(), 1);
1132 
1133             if (xy.pos.indexOf('fr') < 0 &&
1134                 xy.pos.indexOf('%') < 0) {
1135                 // 'px' or numbers are not supported
1136                 lbda = 0;
1137             }
1138 
1139             t = this.minX() + lbda;
1140             x = this.X(t);
1141             y = this.Y(t);
1142             c = (new Coords(Const.COORDS_BY_USER, [x, y], this.board)).scrCoords;
1143 
1144             e = Mat.eps;
1145             if (t < this.minX() + e) {
1146                 dx = (this.X(t + e) - this.X(t)) / e;
1147                 dy = (this.Y(t + e) - this.Y(t)) / e;
1148             } else if (t > this.maxX() - e) {
1149                 dx = (this.X(t) - this.X(t - e)) / e;
1150                 dy = (this.Y(t) - this.Y(t - e)) / e;
1151             } else {
1152                 dx = 0.5 * (this.X(t + e) - this.X(t - e)) / e;
1153                 dy = 0.5 * (this.Y(t + e) - this.Y(t - e)) / e;
1154             }
1155             d = Mat.hypot(dx, dy);
1156 
1157             if (xy.side === 'left') {
1158                 dy *= -1;
1159             } else {
1160                 dx *= -1;
1161             }
1162 
1163             // Position left or right
1164 
1165             if (Type.exists(this.label)) {
1166                 dist = 0.5 * distance / d;
1167             }
1168 
1169             x = c[1] + dy * this.label.size[0] * dist;
1170             y = c[2] - dx * this.label.size[1] * dist;
1171 
1172             return new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board);
1173         },
1174 
1175         // documented in geometry element
1176         getLabelAnchor: function () {
1177             var x, y, pos,
1178                 // xy, lbda, e,
1179                 // t, dx, dy, d,
1180                 // dist = 1.5,
1181                 c,
1182                 ax = 0.05 * this.board.canvasWidth,
1183                 ay = 0.05 * this.board.canvasHeight,
1184                 bx = 0.95 * this.board.canvasWidth,
1185                 by = 0.95 * this.board.canvasHeight;
1186 
1187             if (!Type.exists(this.label)) {
1188                 return new Coords(Const.COORDS_BY_SCREEN, [NaN, NaN], this.board);
1189             }
1190             pos = this.label.evalVisProp('position');
1191             if (!Type.isString(pos)) {
1192                 return new Coords(Const.COORDS_BY_SCREEN, [NaN, NaN], this.board);
1193             }
1194 
1195             if (pos.indexOf('right') < 0 && pos.indexOf('left') < 0) {
1196                 switch (this.evalVisProp('label.position')) {
1197                     case "ulft":
1198                         x = ax;
1199                         y = ay;
1200                         break;
1201                     case "llft":
1202                         x = ax;
1203                         y = by;
1204                         break;
1205                     case "rt":
1206                         x = bx;
1207                         y = 0.5 * by;
1208                         break;
1209                     case "lrt":
1210                         x = bx;
1211                         y = by;
1212                         break;
1213                     case "urt":
1214                         x = bx;
1215                         y = ay;
1216                         break;
1217                     case "top":
1218                         x = 0.5 * bx;
1219                         y = ay;
1220                         break;
1221                     case "bot":
1222                         x = 0.5 * bx;
1223                         y = by;
1224                         break;
1225                     default:
1226                         // includes case 'lft'
1227                         x = ax;
1228                         y = 0.5 * by;
1229                 }
1230             } else {
1231                 // New positioning
1232                 return this.getLabelPosition(pos, this.label.evalVisProp('distance'));
1233                 // xy = Type.parsePosition(pos);
1234                 // lbda = Type.parseNumber(xy.pos, this.maxX() - this.minX(), 1);
1235 
1236                 // if (xy.pos.indexOf('fr') < 0 &&
1237                 //     xy.pos.indexOf('%') < 0) {
1238                 //     // 'px' or numbers are not supported
1239                 //     lbda = 0;
1240                 // }
1241 
1242                 // t = this.minX() + lbda;
1243                 // x = this.X(t);
1244                 // y = this.Y(t);
1245                 // c = (new Coords(Const.COORDS_BY_USER, [x, y], this.board)).scrCoords;
1246 
1247                 // e = Mat.eps;
1248                 // if (t < this.minX() + e) {
1249                 //     dx = (this.X(t + e) - this.X(t)) / e;
1250                 //     dy = (this.Y(t + e) - this.Y(t)) / e;
1251                 // } else if (t > this.maxX() - e) {
1252                 //     dx = (this.X(t) - this.X(t - e)) / e;
1253                 //     dy = (this.Y(t) - this.Y(t - e)) / e;
1254                 // } else {
1255                 //     dx = 0.5 * (this.X(t + e) - this.X(t - e)) / e;
1256                 //     dy = 0.5 * (this.Y(t + e) - this.Y(t - e)) / e;
1257                 // }
1258                 // d = Mat.hypot(dx, dy);
1259 
1260                 // if (xy.side === 'left') {
1261                 //     dy *= -1;
1262                 // } else {
1263                 //     dx *= -1;
1264                 // }
1265 
1266                 // // Position left or right
1267 
1268                 // if (Type.exists(this.label)) {
1269                 //     dist = 0.5 * this.label.evalVisProp('distance') / d;
1270                 // }
1271 
1272                 // x = c[1] + dy * this.label.size[0] * dist;
1273                 // y = c[2] - dx * this.label.size[1] * dist;
1274 
1275                 // return new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board);
1276 
1277             }
1278             c = new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board, false);
1279             return Geometry.projectCoordsToCurve(
1280                 c.usrCoords[1], c.usrCoords[2], 0, this, this.board
1281             )[0];
1282         },
1283 
1284         // documented in geometry element
1285         cloneToBackground: function () {
1286             var er,
1287                 copy = Type.getCloneObject(this);
1288 
1289             copy.points = this.points.slice(0);
1290             copy.bezierDegree = this.bezierDegree;
1291             copy.numberPoints = this.numberPoints;
1292 
1293             er = this.board.renderer.enhancedRendering;
1294             this.board.renderer.enhancedRendering = true;
1295             this.board.renderer.drawCurve(copy);
1296             this.board.renderer.enhancedRendering = er;
1297             this.traces[copy.id] = copy.rendNode;
1298 
1299             return this;
1300         },
1301 
1302         // Already documented in GeometryElement
1303         bounds: function () {
1304             var minX = Infinity,
1305                 maxX = -Infinity,
1306                 minY = Infinity,
1307                 maxY = -Infinity,
1308                 l = this.points.length,
1309                 i,
1310                 bezier,
1311                 up;
1312 
1313             if (this.bezierDegree === 3) {
1314                 // Add methods X(), Y()
1315                 for (i = 0; i < l; i++) {
1316                     this.points[i].X = Type.bind(function () {
1317                         return this.usrCoords[1];
1318                     }, this.points[i]);
1319                     this.points[i].Y = Type.bind(function () {
1320                         return this.usrCoords[2];
1321                     }, this.points[i]);
1322                 }
1323                 bezier = Numerics.bezier(this.points);
1324                 up = bezier[3]();
1325                 minX = Numerics.fminbr(
1326                     function (t) {
1327                         return bezier[0](t);
1328                     },
1329                     [0, up]
1330                 );
1331                 maxX = Numerics.fminbr(
1332                     function (t) {
1333                         return -bezier[0](t);
1334                     },
1335                     [0, up]
1336                 );
1337                 minY = Numerics.fminbr(
1338                     function (t) {
1339                         return bezier[1](t);
1340                     },
1341                     [0, up]
1342                 );
1343                 maxY = Numerics.fminbr(
1344                     function (t) {
1345                         return -bezier[1](t);
1346                     },
1347                     [0, up]
1348                 );
1349 
1350                 minX = bezier[0](minX);
1351                 maxX = bezier[0](maxX);
1352                 minY = bezier[1](minY);
1353                 maxY = bezier[1](maxY);
1354                 return [minX, maxY, maxX, minY];
1355             }
1356 
1357             // Linear segments
1358             for (i = 0; i < l; i++) {
1359                 if (minX > this.points[i].usrCoords[1]) {
1360                     minX = this.points[i].usrCoords[1];
1361                 }
1362 
1363                 if (maxX < this.points[i].usrCoords[1]) {
1364                     maxX = this.points[i].usrCoords[1];
1365                 }
1366 
1367                 if (minY > this.points[i].usrCoords[2]) {
1368                     minY = this.points[i].usrCoords[2];
1369                 }
1370 
1371                 if (maxY < this.points[i].usrCoords[2]) {
1372                     maxY = this.points[i].usrCoords[2];
1373                 }
1374             }
1375 
1376             return [minX, maxY, maxX, minY];
1377         },
1378 
1379         // documented in element.js
1380         getParents: function () {
1381             var p = [this.xterm, this.yterm, this.minX(), this.maxX()];
1382 
1383             if (this.parents.length !== 0) {
1384                 p = this.parents;
1385             }
1386 
1387             return p;
1388         },
1389 
1390         /**
1391          * Shift the curve by the vector 'where'.
1392          *
1393          * @param {Array} where Array containing the x and y coordinate of the target location.
1394          * @returns {JXG.Curve} Reference to itself.
1395          */
1396         moveTo: function (where) {
1397             // TODO add animation
1398             var delta = [],
1399                 p;
1400             if (this.points.length > 0 && !this.evalVisProp('fixed')) {
1401                 p = this.points[0];
1402                 if (where.length === 3) {
1403                     delta = [
1404                         where[0] - p.usrCoords[0],
1405                         where[1] - p.usrCoords[1],
1406                         where[2] - p.usrCoords[2]
1407                     ];
1408                 } else {
1409                     delta = [where[0] - p.usrCoords[1], where[1] - p.usrCoords[2]];
1410                 }
1411                 this.setPosition(Const.COORDS_BY_USER, delta);
1412                 return this.board.update(this);
1413             }
1414             return this;
1415         },
1416 
1417         /**
1418          * If the curve is the result of a transformation applied
1419          * to a continuous curve, the glider projection has to be done
1420          * on the original curve. Otherwise there will be problems
1421          * when changing between high and low precision plotting,
1422          * since there number of points changes.
1423          *
1424          * @private
1425          * @returns {Array} [Boolean, curve]: Array contining 'true' if curve is result of a transformation,
1426          *   and the source curve of the transformation.
1427          */
1428         getTransformationSource: function () {
1429             var isTransformed, curve_org;
1430             if (Type.exists(this._transformationSource)) {
1431                 curve_org = this._transformationSource;
1432                 if (
1433                     curve_org.elementClass === Const.OBJECT_CLASS_CURVE //&&
1434                     //curve_org.evalVisProp('curvetype') !== 'plot'
1435                 ) {
1436                     isTransformed = true;
1437                 }
1438             }
1439             return [isTransformed, curve_org];
1440         }
1441 
1442         // See JXG.Math.Geometry.pnpoly
1443         // pnpoly: function (x_in, y_in, coord_type) {
1444         //     var i,
1445         //         j,
1446         //         len,
1447         //         x,
1448         //         y,
1449         //         crds,
1450         //         v = this.points,
1451         //         isIn = false;
1452 
1453         //     if (coord_type === Const.COORDS_BY_USER) {
1454         //         crds = new Coords(Const.COORDS_BY_USER, [x_in, y_in], this.board);
1455         //         x = crds.scrCoords[1];
1456         //         y = crds.scrCoords[2];
1457         //     } else {
1458         //         x = x_in;
1459         //         y = y_in;
1460         //     }
1461 
1462         //     len = this.points.length;
1463         //     for (i = 0, j = len - 2; i < len - 1; j = i++) {
1464         //         if (
1465         //             v[i].scrCoords[2] > y !== v[j].scrCoords[2] > y &&
1466         //             x <
1467         //                 ((v[j].scrCoords[1] - v[i].scrCoords[1]) * (y - v[i].scrCoords[2])) /
1468         //                     (v[j].scrCoords[2] - v[i].scrCoords[2]) +
1469         //                     v[i].scrCoords[1]
1470         //         ) {
1471         //             isIn = !isIn;
1472         //         }
1473         //     }
1474 
1475         //     return isIn;
1476         // }
1477     }
1478 );
1479 
1480 /**
1481  * @class  Curves can be defined by mappings or by discrete data sets.
1482  * In general, a curve is a mapping from R to R^2, where t maps to (x(t),y(t)). The graph is drawn for t in the interval [a,b].
1483  * <p>
1484  * The following types of curves can be plotted:
1485  * <ul>
1486  *  <li> parametric curves: t mapsto (x(t),y(t)), where x() and y() are univariate functions.
1487  *  <li> polar curves: curves commonly written with polar equations like spirals and cardioids.
1488  *  <li> data plots: plot line segments through a given list of coordinates.
1489  * </ul>
1490  * @pseudo
1491  * @name Curve
1492  * @augments JXG.Curve
1493  * @constructor
1494  * @type Object
1495  * @description JXG.Curve
1496 
1497  * @param {function,number_function,number_function,number_function,number}  x,y,a_,b_ Parent elements for Parametric Curves.
1498  *                     <p>
1499  *                     x describes the x-coordinate of the curve. It may be a function term in one variable, e.g. x(t).
1500  *                     In case of x being of type number, x(t) is set to  a constant function.
1501  *                     this function at the values of the array.
1502  *                     </p>
1503  *                     <p>
1504  *                     y describes the y-coordinate of the curve. In case of a number, y(t) is set to the constant function
1505  *                     returning this number.
1506  *                     </p>
1507  *                     <p>
1508  *                     Further parameters are an optional number or function for the left interval border a,
1509  *                     and an optional number or function for the right interval border b.
1510  *                     </p>
1511  *                     <p>
1512  *                     Default values are a=-10 and b=10.
1513  *                     </p>
1514  *
1515  * @param {array_array,function,number}
1516  *
1517  * @description x,y Parent elements for Data Plots.
1518  *                     <p>
1519  *                     x and y are arrays contining the x and y coordinates of the data points which are connected by
1520  *                     line segments. The individual entries of x and y may also be functions.
1521  *                     In case of x being an array the curve type is data plot, regardless of the second parameter and
1522  *                     if additionally the second parameter y is a function term the data plot evaluates.
1523  *                     </p>
1524  * @param {function_array,function,number_function,number_function,number}
1525  * @description r,offset_,a_,b_ Parent elements for Polar Curves.
1526  *                     <p>
1527  *                     The first parameter is a function term r(phi) describing the polar curve.
1528  *                     </p>
1529  *                     <p>
1530  *                     The second parameter is the offset of the curve. It has to be
1531  *                     an array containing numbers or functions describing the offset. Default value is the origin [0,0].
1532  *                     </p>
1533  *                     <p>
1534  *                     Further parameters are an optional number or function for the left interval border a,
1535  *                     and an optional number or function for the right interval border b.
1536  *                     </p>
1537  *                     <p>
1538  *                     Default values are a=-10 and b=10.
1539  *                     </p>
1540  * <p>
1541  * Additionally, a curve can be created by providing a curve and a transformation (or an array of transformations).
1542  * The result is a curve which is the transformation of the supplied curve.
1543  *
1544  * @see JXG.Curve
1545  * @example
1546  * // Parametric curve
1547  * // Create a curve of the form (t-sin(t), 1-cos(t), i.e.
1548  * // the cycloid curve.
1549  *   var graph = board.create('curve',
1550  *                        [function(t){ return t-Math.sin(t);},
1551  *                         function(t){ return 1-Math.cos(t);},
1552  *                         0, 2*Math.PI]
1553  *                     );
1554  * </pre><div class="jxgbox" id="JXGaf9f818b-f3b6-4c4d-8c4c-e4a4078b726d" style="width: 300px; height: 300px;"></div>
1555  * <script type="text/javascript">
1556  *   var c1_board = JXG.JSXGraph.initBoard('JXGaf9f818b-f3b6-4c4d-8c4c-e4a4078b726d', {boundingbox: [-1, 5, 7, -1], axis: true, showcopyright: false, shownavigation: false});
1557  *   var graph1 = c1_board.create('curve', [function(t){ return t-Math.sin(t);},function(t){ return 1-Math.cos(t);},0, 2*Math.PI]);
1558  * </script><pre>
1559  * @example
1560  * // Data plots
1561  * // Connect a set of points given by coordinates with dashed line segments.
1562  * // The x- and y-coordinates of the points are given in two separate
1563  * // arrays.
1564  *   var x = [0,1,2,3,4,5,6,7,8,9];
1565  *   var y = [9.2,1.3,7.2,-1.2,4.0,5.3,0.2,6.5,1.1,0.0];
1566  *   var graph = board.create('curve', [x,y], {dash:2});
1567  * </pre><div class="jxgbox" id="JXG7dcbb00e-b6ff-481d-b4a8-887f5d8c6a83" style="width: 300px; height: 300px;"></div>
1568  * <script type="text/javascript">
1569  *   var c3_board = JXG.JSXGraph.initBoard('JXG7dcbb00e-b6ff-481d-b4a8-887f5d8c6a83', {boundingbox: [-1,10,10,-1], axis: true, showcopyright: false, shownavigation: false});
1570  *   var x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1571  *   var y = [9.2, 1.3, 7.2, -1.2, 4.0, 5.3, 0.2, 6.5, 1.1, 0.0];
1572  *   var graph3 = c3_board.create('curve', [x,y], {dash:2});
1573  * </script><pre>
1574  * @example
1575  * // Polar plot
1576  * // Create a curve with the equation r(phi)= a*(1+phi), i.e.
1577  * // a cardioid.
1578  *   var a = board.create('slider',[[0,2],[2,2],[0,1,2]]);
1579  *   var graph = board.create('curve',
1580  *                        [function(phi){ return a.Value()*(1-Math.cos(phi));},
1581  *                         [1,0],
1582  *                         0, 2*Math.PI],
1583  *                         {curveType: 'polar'}
1584  *                     );
1585  * </pre><div class="jxgbox" id="JXGd0bc7a2a-8124-45ca-a6e7-142321a8f8c2" style="width: 300px; height: 300px;"></div>
1586  * <script type="text/javascript">
1587  *   var c2_board = JXG.JSXGraph.initBoard('JXGd0bc7a2a-8124-45ca-a6e7-142321a8f8c2', {boundingbox: [-3,3,3,-3], axis: true, showcopyright: false, shownavigation: false});
1588  *   var a = c2_board.create('slider',[[0,2],[2,2],[0,1,2]]);
1589  *   var graph2 = c2_board.create('curve', [function(phi){ return a.Value()*(1-Math.cos(phi));}, [1,0], 0, 2*Math.PI], {curveType: 'polar'});
1590  * </script><pre>
1591  *
1592  * @example
1593  *  // Draggable Bezier curve
1594  *  var col, p, c;
1595  *  col = 'blue';
1596  *  p = [];
1597  *  p.push(board.create('point',[-2, -1 ], {size: 5, strokeColor:col, fillColor:col}));
1598  *  p.push(board.create('point',[1, 2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1599  *  p.push(board.create('point',[-1, -2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1600  *  p.push(board.create('point',[2, -2], {size: 5, strokeColor:col, fillColor:col}));
1601  *
1602  *  c = board.create('curve', JXG.Math.Numerics.bezier(p),
1603  *              {strokeColor:'red', name:"curve", strokeWidth:5, fixed: false}); // Draggable curve
1604  *  c.addParents(p);
1605  * </pre><div class="jxgbox" id="JXG7bcc6280-f6eb-433e-8281-c837c3387849" style="width: 300px; height: 300px;"></div>
1606  * <script type="text/javascript">
1607  * (function(){
1608  *  var board, col, p, c;
1609  *  board = JXG.JSXGraph.initBoard('JXG7bcc6280-f6eb-433e-8281-c837c3387849', {boundingbox: [-3,3,3,-3], axis: true, showcopyright: false, shownavigation: false});
1610  *  col = 'blue';
1611  *  p = [];
1612  *  p.push(board.create('point',[-2, -1 ], {size: 5, strokeColor:col, fillColor:col}));
1613  *  p.push(board.create('point',[1, 2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1614  *  p.push(board.create('point',[-1, -2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1615  *  p.push(board.create('point',[2, -2], {size: 5, strokeColor:col, fillColor:col}));
1616  *
1617  *  c = board.create('curve', JXG.Math.Numerics.bezier(p),
1618  *              {strokeColor:'red', name:"curve", strokeWidth:5, fixed: false}); // Draggable curve
1619  *  c.addParents(p);
1620  * })();
1621  * </script><pre>
1622  *
1623  * @example
1624  *         // The curve cu2 is the reflection of cu1 against line li
1625  *         var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1626  *         var reflect = board.create('transform', [li], {type: 'reflect'});
1627  *         var cu1 = board.create('curve', [[-1, -1, -0.5, -1, -1, -0.5], [-3, -2, -2, -2, -2.5, -2.5]]);
1628  *         var cu2 = board.create('curve', [cu1, reflect], {strokeColor: 'red'});
1629  *
1630  * </pre><div id="JXG866dc7a2-d448-11e7-93b3-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
1631  * <script type="text/javascript">
1632  *     (function() {
1633  *         var board = JXG.JSXGraph.initBoard('JXG866dc7a2-d448-11e7-93b3-901b0e1b8723',
1634  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1635  *             var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1636  *             var reflect = board.create('transform', [li], {type: 'reflect'});
1637  *             var cu1 = board.create('curve', [[-1, -1, -0.5, -1, -1, -0.5], [-3, -2, -2, -2, -2.5, -2.5]]);
1638  *             var cu2 = board.create('curve', [cu1, reflect], {strokeColor: 'red'});
1639  *
1640  *     })();
1641  *
1642  * </script><pre>
1643  */
1644 JXG.createCurve = function (board, parents, attributes) {
1645     var obj,
1646         cu,
1647         attr = Type.copyAttributes(attributes, board.options, "curve");
1648 
1649     obj = board.select(parents[0], true);
1650     if (
1651         Type.isTransformationOrArray(parents[1]) &&
1652         Type.isObject(obj) &&
1653         (obj.type === Const.OBJECT_TYPE_CURVE ||
1654             obj.type === Const.OBJECT_TYPE_ANGLE ||
1655             obj.type === Const.OBJECT_TYPE_ARC ||
1656             obj.type === Const.OBJECT_TYPE_CONIC ||
1657             obj.type === Const.OBJECT_TYPE_SECTOR)
1658     ) {
1659         if (obj.type === Const.OBJECT_TYPE_SECTOR) {
1660             attr = Type.copyAttributes(attributes, board.options, "sector");
1661         } else if (obj.type === Const.OBJECT_TYPE_ARC) {
1662             attr = Type.copyAttributes(attributes, board.options, "arc");
1663         } else if (obj.type === Const.OBJECT_TYPE_ANGLE) {
1664             if (!Type.exists(attributes.withLabel)) {
1665                 attributes.withLabel = false;
1666             }
1667             attr = Type.copyAttributes(attributes, board.options, "angle");
1668         } else {
1669             attr = Type.copyAttributes(attributes, board.options, "curve");
1670         }
1671         attr = Type.copyAttributes(attr, board.options, "curve");
1672 
1673         cu = new JXG.Curve(board, ["x", [], []], attr);
1674         /**
1675          * @class
1676          * @ignore
1677          */
1678         cu.updateDataArray = function () {
1679             var i,
1680                 le = obj.numberPoints;
1681             this.bezierDegree = obj.bezierDegree;
1682             this.dataX = [];
1683             this.dataY = [];
1684             for (i = 0; i < le; i++) {
1685                 this.dataX.push(obj.points[i].usrCoords[1]);
1686                 this.dataY.push(obj.points[i].usrCoords[2]);
1687             }
1688             return this;
1689         };
1690         cu.addTransform(parents[1]);
1691         obj.addChild(cu);
1692         cu.setParents([obj]);
1693         cu._transformationSource = obj;
1694 
1695         return cu;
1696     }
1697     attr = Type.copyAttributes(attributes, board.options, "curve");
1698     return new JXG.Curve(board, ["x"].concat(parents), attr);
1699 };
1700 
1701 JXG.registerElement("curve", JXG.createCurve);
1702 
1703 /**
1704  * @class A functiongraph visualizes a map x → f(x).
1705  * The graph is displayed for x in the interval [a,b] and is a {@link Curve} element.
1706  * @pseudo
1707  * @name Functiongraph
1708  * @augments JXG.Curve
1709  * @constructor
1710  * @type JXG.Curve
1711  * @param {function_number,function_number,function} f,a_,b_ Parent elements are a function term f(x) describing the function graph.
1712  *         <p>
1713  *         Further, an optional number or function for the left interval border a,
1714  *         and an optional number or function for the right interval border b.
1715  *         <p>
1716  *         Default values are a=-10 and b=10.
1717  * @see JXG.Curve
1718  * @example
1719  * // Create a function graph for f(x) = 0.5*x*x-2*x
1720  *   var graph = board.create('functiongraph',
1721  *                        [function(x){ return 0.5*x*x-2*x;}, -2, 4]
1722  *                     );
1723  * </pre><div class="jxgbox" id="JXGefd432b5-23a3-4846-ac5b-b471e668b437" style="width: 300px; height: 300px;"></div>
1724  * <script type="text/javascript">
1725  *   var alex1_board = JXG.JSXGraph.initBoard('JXGefd432b5-23a3-4846-ac5b-b471e668b437', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
1726  *   var graph = alex1_board.create('functiongraph', [function(x){ return 0.5*x*x-2*x;}, -2, 4]);
1727  * </script><pre>
1728  * @example
1729  * // Create a function graph for f(x) = 0.5*x*x-2*x with variable interval
1730  *   var s = board.create('slider',[[0,4],[3,4],[-2,4,5]]);
1731  *   var graph = board.create('functiongraph',
1732  *                        [function(x){ return 0.5*x*x-2*x;},
1733  *                         -2,
1734  *                         function(){return s.Value();}]
1735  *                     );
1736  * </pre><div class="jxgbox" id="JXG4a203a84-bde5-4371-ad56-44619690bb50" style="width: 300px; height: 300px;"></div>
1737  * <script type="text/javascript">
1738  *   var alex2_board = JXG.JSXGraph.initBoard('JXG4a203a84-bde5-4371-ad56-44619690bb50', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
1739  *   var s = alex2_board.create('slider',[[0,4],[3,4],[-2,4,5]]);
1740  *   var graph = alex2_board.create('functiongraph', [function(x){ return 0.5*x*x-2*x;}, -2, function(){return s.Value();}]);
1741  * </script><pre>
1742  */
1743 JXG.createFunctiongraph = function (board, parents, attributes) {
1744     var attr,
1745         par = ["x", "x"].concat(parents); // variable name and identity function for x-coordinate
1746     // par = ["x", function(x) { return x; }].concat(parents);
1747 
1748     attr = Type.copyAttributes(attributes, board.options, "functiongraph");
1749     attr = Type.copyAttributes(attr, board.options, "curve");
1750     attr.curvetype = "functiongraph";
1751     return new JXG.Curve(board, par, attr);
1752 };
1753 
1754 JXG.registerElement("functiongraph", JXG.createFunctiongraph);
1755 JXG.registerElement("plot", JXG.createFunctiongraph);
1756 
1757 /**
1758  * @class The (natural) cubic spline curves (function graph) interpolating a set of points.
1759  * Create a dynamic spline interpolated curve given by sample points p_1 to p_n.
1760  * @pseudo
1761  * @name Spline
1762  * @augments JXG.Curve
1763  * @constructor
1764  * @type JXG.Curve
1765  * @param {JXG.Board} board Reference to the board the spline is drawn on.
1766  * @param {Array} parents Array of points the spline interpolates. This can be
1767  *   <ul>
1768  *   <li> an array of JSXGraph points</li>
1769  *   <li> an array of coordinate pairs</li>
1770  *   <li> an array of functions returning coordinate pairs</li>
1771  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
1772  *   </ul>
1773  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
1774  * @param {Object} attributes Define color, width, ... of the spline
1775  * @returns {JXG.Curve} Returns reference to an object of type JXG.Curve.
1776  * @see JXG.Curve
1777  * @example
1778  *
1779  * var p = [];
1780  * p[0] = board.create('point', [-2,2], {size: 4, face: 'o'});
1781  * p[1] = board.create('point', [0,-1], {size: 4, face: 'o'});
1782  * p[2] = board.create('point', [2,0], {size: 4, face: 'o'});
1783  * p[3] = board.create('point', [4,1], {size: 4, face: 'o'});
1784  *
1785  * var c = board.create('spline', p, {strokeWidth:3});
1786  * </pre><div id="JXG6c197afc-e482-11e5-b1bf-901b0e1b8723" style="width: 300px; height: 300px;"></div>
1787  * <script type="text/javascript">
1788  *     (function() {
1789  *         var board = JXG.JSXGraph.initBoard('JXG6c197afc-e482-11e5-b1bf-901b0e1b8723',
1790  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1791  *
1792  *     var p = [];
1793  *     p[0] = board.create('point', [-2,2], {size: 4, face: 'o'});
1794  *     p[1] = board.create('point', [0,-1], {size: 4, face: 'o'});
1795  *     p[2] = board.create('point', [2,0], {size: 4, face: 'o'});
1796  *     p[3] = board.create('point', [4,1], {size: 4, face: 'o'});
1797  *
1798  *     var c = board.create('spline', p, {strokeWidth:3});
1799  *     })();
1800  *
1801  * </script><pre>
1802  *
1803  */
1804 JXG.createSpline = function (board, parents, attributes) {
1805     var el, funcs, ret;
1806 
1807     funcs = function () {
1808         var D,
1809             x = [],
1810             y = [];
1811 
1812         return [
1813             function (t, suspended) {
1814                 // Function term
1815                 var i, j, c;
1816 
1817                 if (!suspended) {
1818                     x = [];
1819                     y = [];
1820 
1821                     // given as [x[], y[]]
1822                     if (
1823                         parents.length === 2 &&
1824                         Type.isArray(parents[0]) &&
1825                         Type.isArray(parents[1]) &&
1826                         parents[0].length === parents[1].length
1827                     ) {
1828                         for (i = 0; i < parents[0].length; i++) {
1829                             if (Type.isFunction(parents[0][i])) {
1830                                 x.push(parents[0][i]());
1831                             } else {
1832                                 x.push(parents[0][i]);
1833                             }
1834 
1835                             if (Type.isFunction(parents[1][i])) {
1836                                 y.push(parents[1][i]());
1837                             } else {
1838                                 y.push(parents[1][i]);
1839                             }
1840                         }
1841                     } else {
1842                         for (i = 0; i < parents.length; i++) {
1843                             if (Type.isPoint(parents[i])) {
1844                                 x.push(parents[i].X());
1845                                 y.push(parents[i].Y());
1846                                 // given as [[x1,y1], [x2, y2], ...]
1847                             } else if (Type.isArray(parents[i]) && parents[i].length === 2) {
1848                                 for (j = 0; j < parents.length; j++) {
1849                                     if (Type.isFunction(parents[j][0])) {
1850                                         x.push(parents[j][0]());
1851                                     } else {
1852                                         x.push(parents[j][0]);
1853                                     }
1854 
1855                                     if (Type.isFunction(parents[j][1])) {
1856                                         y.push(parents[j][1]());
1857                                     } else {
1858                                         y.push(parents[j][1]);
1859                                     }
1860                                 }
1861                             } else if (
1862                                 Type.isFunction(parents[i]) &&
1863                                 parents[i]().length === 2
1864                             ) {
1865                                 c = parents[i]();
1866                                 x.push(c[0]);
1867                                 y.push(c[1]);
1868                             }
1869                         }
1870                     }
1871 
1872                     // The array D has only to be calculated when the position of one or more sample points
1873                     // changes. Otherwise D is always the same for all points on the spline.
1874                     D = Numerics.splineDef(x, y);
1875                 }
1876 
1877                 return Numerics.splineEval(t, x, y, D);
1878             },
1879             // minX()
1880             function () {
1881                 return x[0];
1882             },
1883             //maxX()
1884             function () {
1885                 return x[x.length - 1];
1886             }
1887         ];
1888     };
1889 
1890     attributes = Type.copyAttributes(attributes, board.options, "curve");
1891     attributes.curvetype = "functiongraph";
1892     ret = funcs();
1893     el = new JXG.Curve(board, ["x", "x", ret[0], ret[1], ret[2]], attributes);
1894     el.setParents(parents);
1895     el.elType = "spline";
1896 
1897     return el;
1898 };
1899 
1900 /**
1901  * Register the element type spline at JSXGraph
1902  * @private
1903  */
1904 JXG.registerElement("spline", JXG.createSpline);
1905 
1906 /**
1907  * @class Cardinal spline curve through a given data set.
1908  * Create a dynamic cardinal spline interpolated curve given by sample points p_1 to p_n.
1909  * @pseudo
1910  * @name Cardinalspline
1911  * @augments JXG.Curve
1912  * @constructor
1913  * @type JXG.Curve
1914  * @param {Array} points Points array defining the cardinal spline. This can be
1915  *   <ul>
1916  *   <li> an array of JSXGraph points</li>
1917  *   <li> an array of coordinate pairs</li>
1918  *   <li> an array of functions returning coordinate pairs</li>
1919  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
1920  *   </ul>
1921  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
1922  * @param {function,Number} tau Tension parameter
1923  * @param {String} [type='uniform'] Type of the cardinal spline, may be 'uniform' (default) or 'centripetal'
1924  * @see JXG.Curve
1925  * @example
1926  * //Create a cardinal spline out of an array of JXG points with adjustable tension
1927  *
1928  * //Create array of points
1929  * var p = [];
1930  * p.push(board.create('point',[0,0]));
1931  * p.push(board.create('point',[1,4]));
1932  * p.push(board.create('point',[4,5]));
1933  * p.push(board.create('point',[2,3]));
1934  * p.push(board.create('point',[3,0]));
1935  *
1936  * // tension
1937  * var tau = board.create('slider', [[-4,-5],[2,-5],[0.001,0.5,1]], {name:'tau'});
1938  * var c = board.create('cardinalspline', [p, function(){ return tau.Value();}], {strokeWidth:3});
1939  *
1940  * </pre><div id="JXG1537cb69-4d45-43aa-8fc3-c6d4f98b4cdd" class="jxgbox" style="width: 300px; height: 300px;"></div>
1941  * <script type="text/javascript">
1942  *     (function() {
1943  *         var board = JXG.JSXGraph.initBoard('JXG1537cb69-4d45-43aa-8fc3-c6d4f98b4cdd',
1944  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1945  *     //Create a cardinal spline out of an array of JXG points with adjustable tension
1946  *
1947  *     //Create array of points
1948  *     var p = [];
1949  *     p.push(board.create('point',[0,0]));
1950  *     p.push(board.create('point',[1,4]));
1951  *     p.push(board.create('point',[4,5]));
1952  *     p.push(board.create('point',[2,3]));
1953  *     p.push(board.create('point',[3,0]));
1954  *
1955  *     // tension
1956  *     var tau = board.create('slider', [[-4,-5],[2,-5],[0.001,0.5,1]], {name:'tau'});
1957  *     var c = board.create('cardinalspline', [p, function(){ return tau.Value();}], {strokeWidth:3});
1958  *
1959  *     })();
1960  *
1961  * </script><pre>
1962  *
1963  */
1964 JXG.createCardinalSpline = function (board, parents, attributes) {
1965     var el,
1966         getPointLike,
1967         points,
1968         tau,
1969         type,
1970         p,
1971         q,
1972         i,
1973         le,
1974         splineArr,
1975         errStr = "\nPossible parent types: [points:array, tau:number|function, type:string]";
1976 
1977     if (!Type.exists(parents[0]) || !Type.isArray(parents[0])) {
1978         throw new Error(
1979             "JSXGraph: JXG.createCardinalSpline: argument 1 'points' has to be array of points or coordinate pairs" +
1980             errStr
1981         );
1982     }
1983     if (
1984         !Type.exists(parents[1]) ||
1985         (!Type.isNumber(parents[1]) && !Type.isFunction(parents[1]))
1986     ) {
1987         throw new Error(
1988             "JSXGraph: JXG.createCardinalSpline: argument 2 'tau' has to be number between [0,1] or function'" +
1989             errStr
1990         );
1991     }
1992     if (!Type.exists(parents[2]) || !Type.isString(parents[2])) {
1993         type = 'uniform';
1994         // throw new Error(
1995         //     "JSXGraph: JXG.createCardinalSpline: argument 3 'type' has to be string 'uniform' or 'centripetal'" +
1996         //     errStr
1997         // );
1998     } else {
1999         type = parents[2];
2000     }
2001 
2002     attributes = Type.copyAttributes(attributes, board.options, "curve");
2003     attributes = Type.copyAttributes(attributes, board.options, "cardinalspline");
2004     attributes.curvetype = "parameter";
2005 
2006     p = parents[0];
2007     q = [];
2008 
2009     // Given as [x[], y[]]
2010     if (
2011         !attributes.isarrayofcoordinates &&
2012         p.length === 2 &&
2013         Type.isArray(p[0]) &&
2014         Type.isArray(p[1]) &&
2015         p[0].length === p[1].length
2016     ) {
2017         for (i = 0; i < p[0].length; i++) {
2018             q[i] = [];
2019             if (Type.isFunction(p[0][i])) {
2020                 q[i].push(p[0][i]());
2021             } else {
2022                 q[i].push(p[0][i]);
2023             }
2024 
2025             if (Type.isFunction(p[1][i])) {
2026                 q[i].push(p[1][i]());
2027             } else {
2028                 q[i].push(p[1][i]);
2029             }
2030         }
2031     } else {
2032         // given as [[x0, y0], [x1, y1], point, ...]
2033         for (i = 0; i < p.length; i++) {
2034             if (Type.isString(p[i])) {
2035                 q.push(board.select(p[i]));
2036             } else if (Type.isPoint(p[i])) {
2037                 q.push(p[i]);
2038                 // given as [[x0,y0], [x1, y2], ...]
2039             } else if (Type.isArray(p[i]) && p[i].length === 2) {
2040                 q[i] = [];
2041                 if (Type.isFunction(p[i][0])) {
2042                     q[i].push(p[i][0]());
2043                 } else {
2044                     q[i].push(p[i][0]);
2045                 }
2046 
2047                 if (Type.isFunction(p[i][1])) {
2048                     q[i].push(p[i][1]());
2049                 } else {
2050                     q[i].push(p[i][1]);
2051                 }
2052             } else if (Type.isFunction(p[i]) && p[i]().length === 2) {
2053                 q.push(parents[i]());
2054             }
2055         }
2056     }
2057 
2058     if (attributes.createpoints === true) {
2059         points = Type.providePoints(board, q, attributes, "cardinalspline", ["points"]);
2060     } else {
2061         points = [];
2062 
2063         /**
2064          * @ignore
2065          */
2066         getPointLike = function (ii) {
2067             return {
2068                 X: function () {
2069                     return q[ii][0];
2070                 },
2071                 Y: function () {
2072                     return q[ii][1];
2073                 },
2074                 Dist: function (p) {
2075                     var dx = this.X() - p.X(),
2076                         dy = this.Y() - p.Y();
2077 
2078                     return Mat.hypot(dx, dy);
2079                 }
2080             };
2081         };
2082 
2083         for (i = 0; i < q.length; i++) {
2084             if (Type.isPoint(q[i])) {
2085                 points.push(q[i]);
2086             } else {
2087                 points.push(getPointLike(i));
2088             }
2089         }
2090     }
2091 
2092     tau = parents[1];
2093     // type = parents[2];
2094 
2095     splineArr = ["x"].concat(Numerics.CardinalSpline(points, tau, type));
2096 
2097     el = new JXG.Curve(board, splineArr, attributes);
2098     le = points.length;
2099     el.setParents(points);
2100     for (i = 0; i < le; i++) {
2101         p = points[i];
2102         if (Type.isPoint(p)) {
2103             if (Type.exists(p._is_new)) {
2104                 el.addChild(p);
2105                 delete p._is_new;
2106             } else {
2107                 p.addChild(el);
2108             }
2109         }
2110     }
2111     el.elType = "cardinalspline";
2112 
2113     return el;
2114 };
2115 
2116 /**
2117  * Register the element type cardinalspline at JSXGraph
2118  * @private
2119  */
2120 JXG.registerElement("cardinalspline", JXG.createCardinalSpline);
2121 
2122 /**
2123  * @class Interpolate data points by the spline curve from Metapost (by Donald Knuth and John Hobby).
2124  * Create a dynamic metapost spline interpolated curve given by sample points p_1 to p_n.
2125  * @pseudo
2126  * @name Metapostspline
2127  * @augments JXG.Curve
2128  * @constructor
2129  * @type JXG.Curve
2130  * @param {JXG.Board} board Reference to the board the metapost spline is drawn on.
2131  * @param {Array} parents Array with two entries.
2132  * <p>
2133  *   First entry: Array of points the spline interpolates. This can be
2134  *   <ul>
2135  *   <li> an array of JSXGraph points</li>
2136  *   <li> an object of coordinate pairs</li>
2137  *   <li> an array of functions returning coordinate pairs</li>
2138  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
2139  *   </ul>
2140  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
2141  *   <p>
2142  *   Second entry: JavaScript object containing the control values like tension, direction, curl.
2143  * @param {Object} attributes Define color, width, ... of the metapost spline
2144  * @returns {JXG.Curve} Returns reference to an object of type JXG.Curve.
2145  * @see JXG.Curve
2146  * @example
2147  *     var po = [],
2148  *         attr = {
2149  *             size: 5,
2150  *             color: 'red'
2151  *         },
2152  *         controls;
2153  *
2154  *     var tension = board.create('slider', [[-3, 6], [3, 6], [0, 1, 20]], {name: 'tension'});
2155  *     var curl = board.create('slider', [[-3, 5], [3, 5], [0, 1, 30]], {name: 'curl A, D'});
2156  *     var dir = board.create('slider', [[-3, 4], [3, 4], [-180, 0, 180]], {name: 'direction B'});
2157  *
2158  *     po.push(board.create('point', [-3, -3]));
2159  *     po.push(board.create('point', [0, -3]));
2160  *     po.push(board.create('point', [4, -5]));
2161  *     po.push(board.create('point', [6, -2]));
2162  *
2163  *     var controls = {
2164  *         tension: function() {return tension.Value(); },
2165  *         direction: { 1: function() {return dir.Value(); } },
2166  *         curl: { 0: function() {return curl.Value(); },
2167  *                 3: function() {return curl.Value(); }
2168  *             },
2169  *         isClosed: false
2170  *     };
2171  *
2172  *     // Plot a metapost curve
2173  *     var cu = board.create('metapostspline', [po, controls], {strokeColor: 'blue', strokeWidth: 2});
2174  *
2175  *
2176  * </pre><div id="JXGb8c6ffed-7419-41a3-9e55-3754b2327ae9" class="jxgbox" style="width: 300px; height: 300px;"></div>
2177  * <script type="text/javascript">
2178  *     (function() {
2179  *         var board = JXG.JSXGraph.initBoard('JXGb8c6ffed-7419-41a3-9e55-3754b2327ae9',
2180  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2181  *         var po = [],
2182  *             attr = {
2183  *                 size: 5,
2184  *                 color: 'red'
2185  *             },
2186  *             controls;
2187  *
2188  *         var tension = board.create('slider', [[-3, 6], [3, 6], [0, 1, 20]], {name: 'tension'});
2189  *         var curl = board.create('slider', [[-3, 5], [3, 5], [0, 1, 30]], {name: 'curl A, D'});
2190  *         var dir = board.create('slider', [[-3, 4], [3, 4], [-180, 0, 180]], {name: 'direction B'});
2191  *
2192  *         po.push(board.create('point', [-3, -3]));
2193  *         po.push(board.create('point', [0, -3]));
2194  *         po.push(board.create('point', [4, -5]));
2195  *         po.push(board.create('point', [6, -2]));
2196  *
2197  *         var controls = {
2198  *             tension: function() {return tension.Value(); },
2199  *             direction: { 1: function() {return dir.Value(); } },
2200  *             curl: { 0: function() {return curl.Value(); },
2201  *                     3: function() {return curl.Value(); }
2202  *                 },
2203  *             isClosed: false
2204  *         };
2205  *
2206  *         // Plot a metapost curve
2207  *         var cu = board.create('metapostspline', [po, controls], {strokeColor: 'blue', strokeWidth: 2});
2208  *
2209  *
2210  *     })();
2211  *
2212  * </script><pre>
2213  *
2214  */
2215 JXG.createMetapostSpline = function (board, parents, attributes) {
2216     var el,
2217         getPointLike,
2218         points,
2219         controls,
2220         p,
2221         q,
2222         i,
2223         le,
2224         errStr = "\nPossible parent types: [points:array, controls:object";
2225 
2226     if (!Type.exists(parents[0]) || !Type.isArray(parents[0])) {
2227         throw new Error(
2228             "JSXGraph: JXG.createMetapostSpline: argument 1 'points' has to be array of points or coordinate pairs" +
2229             errStr
2230         );
2231     }
2232     if (!Type.exists(parents[1]) || !Type.isObject(parents[1])) {
2233         throw new Error(
2234             "JSXGraph: JXG.createMetapostSpline: argument 2 'controls' has to be a JavaScript object'" +
2235             errStr
2236         );
2237     }
2238 
2239     attributes = Type.copyAttributes(attributes, board.options, "curve");
2240     attributes = Type.copyAttributes(attributes, board.options, "metapostspline");
2241     attributes.curvetype = "parameter";
2242 
2243     p = parents[0];
2244     q = [];
2245 
2246     // given as [x[], y[]]
2247     if (
2248         !attributes.isarrayofcoordinates &&
2249         p.length === 2 &&
2250         Type.isArray(p[0]) &&
2251         Type.isArray(p[1]) &&
2252         p[0].length === p[1].length
2253     ) {
2254         for (i = 0; i < p[0].length; i++) {
2255             q[i] = [];
2256             if (Type.isFunction(p[0][i])) {
2257                 q[i].push(p[0][i]());
2258             } else {
2259                 q[i].push(p[0][i]);
2260             }
2261 
2262             if (Type.isFunction(p[1][i])) {
2263                 q[i].push(p[1][i]());
2264             } else {
2265                 q[i].push(p[1][i]);
2266             }
2267         }
2268     } else {
2269         // given as [[x0, y0], [x1, y1], point, ...]
2270         for (i = 0; i < p.length; i++) {
2271             if (Type.isString(p[i])) {
2272                 q.push(board.select(p[i]));
2273             } else if (Type.isPoint(p[i])) {
2274                 q.push(p[i]);
2275                 // given as [[x0,y0], [x1, y2], ...]
2276             } else if (Type.isArray(p[i]) && p[i].length === 2) {
2277                 q[i] = [];
2278                 if (Type.isFunction(p[i][0])) {
2279                     q[i].push(p[i][0]());
2280                 } else {
2281                     q[i].push(p[i][0]);
2282                 }
2283 
2284                 if (Type.isFunction(p[i][1])) {
2285                     q[i].push(p[i][1]());
2286                 } else {
2287                     q[i].push(p[i][1]);
2288                 }
2289             } else if (Type.isFunction(p[i]) && p[i]().length === 2) {
2290                 q.push(parents[i]());
2291             }
2292         }
2293     }
2294 
2295     if (attributes.createpoints === true) {
2296         points = Type.providePoints(board, q, attributes, 'metapostspline', ['points']);
2297     } else {
2298         points = [];
2299 
2300         /**
2301          * @ignore
2302          */
2303         getPointLike = function (ii) {
2304             return {
2305                 X: function () {
2306                     return q[ii][0];
2307                 },
2308                 Y: function () {
2309                     return q[ii][1];
2310                 }
2311             };
2312         };
2313 
2314         for (i = 0; i < q.length; i++) {
2315             if (Type.isPoint(q[i])) {
2316                 points.push(q[i]);
2317             } else {
2318                 points.push(getPointLike);
2319             }
2320         }
2321     }
2322 
2323     controls = parents[1];
2324 
2325     el = new JXG.Curve(board, ["t", [], [], 0, p.length - 1], attributes);
2326     /**
2327      * @class
2328      * @ignore
2329      */
2330     el.updateDataArray = function () {
2331         var res,
2332             i,
2333             len = points.length,
2334             p = [];
2335 
2336         for (i = 0; i < len; i++) {
2337             p.push([points[i].X(), points[i].Y()]);
2338         }
2339 
2340         res = Metapost.curve(p, controls);
2341         this.dataX = res[0];
2342         this.dataY = res[1];
2343     };
2344     el.bezierDegree = 3;
2345 
2346     le = points.length;
2347     el.setParents(points);
2348     for (i = 0; i < le; i++) {
2349         if (Type.isPoint(points[i])) {
2350             points[i].addChild(el);
2351         }
2352     }
2353     el.elType = "metapostspline";
2354 
2355     return el;
2356 };
2357 
2358 JXG.registerElement("metapostspline", JXG.createMetapostSpline);
2359 
2360 /**
2361  * @class Visualize the Riemann sum which is an approximation of an integral by a finite sum.
2362  * It is realized as a special curve.
2363  * The returned element has the method Value() which returns the sum of the areas of the bars.
2364  * <p>
2365  * In case of type "simpson" and "trapezoidal", the horizontal line approximating the function value
2366  * is replaced by a parabola or a secant. IN case of "simpson",
2367  * the parabola is approximated visually by a polygonal chain of fixed step width.
2368  *
2369  * @pseudo
2370  * @name Riemannsum
2371  * @augments JXG.Curve
2372  * @constructor
2373  * @type Curve
2374  * @param {function,array_number,function_string,function_function,number_function,number} f,n,type_,a_,b_ Parent elements of Riemannsum are a
2375  *         Either a function term f(x) describing the function graph which is filled by the Riemann bars, or
2376  *         an array consisting of two functions and the area between is filled by the Riemann bars.
2377  *         <p>
2378  *         n determines the number of bars, it is either a fixed number or a function.
2379  *         <p>
2380  *         type is a string or function returning one of the values:  'left', 'right', 'middle', 'lower', 'upper', 'random', 'simpson', or 'trapezoidal'.
2381  *         Default value is 'left'. "simpson" is Simpson's 1/3 rule.
2382  *         <p>
2383  *         Further parameters are an optional number or function for the left interval border a,
2384  *         and an optional number or function for the right interval border b.
2385  *         <p>
2386  *         Default values are a=-10 and b=10.
2387  * @see JXG.Curve
2388  * @example
2389  * // Create Riemann sums for f(x) = 0.5*x*x-2*x.
2390  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2391  *   var f = function(x) { return 0.5*x*x-2*x; };
2392  *   var r = board.create('riemannsum',
2393  *               [f, function(){return s.Value();}, 'upper', -2, 5],
2394  *               {fillOpacity:0.4}
2395  *               );
2396  *   var g = board.create('functiongraph',[f, -2, 5]);
2397  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2398  * </pre><div class="jxgbox" id="JXG940f40cc-2015-420d-9191-c5d83de988cf" style="width: 300px; height: 300px;"></div>
2399  * <script type="text/javascript">
2400  * (function(){
2401  *   var board = JXG.JSXGraph.initBoard('JXG940f40cc-2015-420d-9191-c5d83de988cf', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
2402  *   var f = function(x) { return 0.5*x*x-2*x; };
2403  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2404  *   var r = board.create('riemannsum', [f, function(){return s.Value();}, 'upper', -2, 5], {fillOpacity:0.4});
2405  *   var g = board.create('functiongraph', [f, -2, 5]);
2406  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2407  * })();
2408  * </script><pre>
2409  *
2410  * @example
2411  *   // Riemann sum between two functions
2412  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2413  *   var g = function(x) { return 0.5*x*x-2*x; };
2414  *   var f = function(x) { return -x*(x-4); };
2415  *   var r = board.create('riemannsum',
2416  *               [[g,f], function(){return s.Value();}, 'lower', 0, 4],
2417  *               {fillOpacity:0.4}
2418  *               );
2419  *   var f = board.create('functiongraph',[f, -2, 5]);
2420  *   var g = board.create('functiongraph',[g, -2, 5]);
2421  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2422  * </pre><div class="jxgbox" id="JXGf9a7ba38-b50f-4a32-a873-2f3bf9caee79" style="width: 300px; height: 300px;"></div>
2423  * <script type="text/javascript">
2424  * (function(){
2425  *   var board = JXG.JSXGraph.initBoard('JXGf9a7ba38-b50f-4a32-a873-2f3bf9caee79', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
2426  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2427  *   var g = function(x) { return 0.5*x*x-2*x; };
2428  *   var f = function(x) { return -x*(x-4); };
2429  *   var r = board.create('riemannsum',
2430  *               [[g,f], function(){return s.Value();}, 'lower', 0, 4],
2431  *               {fillOpacity:0.4}
2432  *               );
2433  *   var f = board.create('functiongraph',[f, -2, 5]);
2434  *   var g = board.create('functiongraph',[g, -2, 5]);
2435  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2436  * })();
2437  * </script><pre>
2438  */
2439 JXG.createRiemannsum = function (board, parents, attributes) {
2440     var n, type, f, par, c, attr;
2441 
2442     attr = Type.copyAttributes(attributes, board.options, "riemannsum");
2443     attr.curvetype = "plot";
2444 
2445     f = parents[0];
2446     n = Type.createFunction(parents[1], board, "");
2447 
2448     if (!Type.exists(n)) {
2449         throw new Error(
2450             "JSXGraph: JXG.createRiemannsum: argument '2' n has to be number or function." +
2451             "\nPossible parent types: [function,n:number|function,type,start:number|function,end:number|function]"
2452         );
2453     }
2454 
2455     if (typeof parents[2] === 'string') {
2456         parents[2] = '\'' + parents[2] + '\'';
2457     }
2458 
2459     type = Type.createFunction(parents[2], board, "");
2460     if (!Type.exists(type)) {
2461         throw new Error(
2462             "JSXGraph: JXG.createRiemannsum: argument 3 'type' has to be string or function." +
2463             "\nPossible parent types: [function,n:number|function,type,start:number|function,end:number|function]"
2464         );
2465     }
2466 
2467     par = [[0], [0]].concat(parents.slice(3));
2468 
2469     c = board.create("curve", par, attr);
2470 
2471     c.sum = 0.0;
2472     /**
2473      * Returns the value of the Riemann sum, i.e. the sum of the (signed) areas of the rectangles.
2474      * @name Value
2475      * @memberOf Riemannsum.prototype
2476      * @function
2477      * @returns {Number} value of Riemann sum.
2478      */
2479     c.Value = function () {
2480         return this.sum;
2481     };
2482 
2483     /**
2484      * @class
2485      * @ignore
2486      */
2487     c.updateDataArray = function () {
2488         var u = Numerics.riemann(f, n(), type(), this.minX(), this.maxX());
2489         this.dataX = u[0];
2490         this.dataY = u[1];
2491 
2492         // Update "Riemann sum"
2493         this.sum = u[2];
2494     };
2495 
2496     c.addParentsFromJCFunctions([n, type]);
2497 
2498     return c;
2499 };
2500 
2501 JXG.registerElement("riemannsum", JXG.createRiemannsum);
2502 
2503 /**
2504  * @class A trace curve is simple locus curve showing the orbit of a point that depends on a glider point.
2505  * @pseudo
2506  * @name Tracecurve
2507  * @augments JXG.Curve
2508  * @constructor
2509  * @type Object
2510  * @descript JXG.Curve
2511  * @param {Point} Parent elements of Tracecurve are a
2512  *         glider point and a point whose locus is traced.
2513  * @param {point}
2514  * @see JXG.Curve
2515  * @example
2516  * // Create trace curve.
2517  * var c1 = board.create('circle',[[0, 0], [2, 0]]),
2518  * p1 = board.create('point',[-3, 1]),
2519  * g1 = board.create('glider',[2, 1, c1]),
2520  * s1 = board.create('segment',[g1, p1]),
2521  * p2 = board.create('midpoint',[s1]),
2522  * curve = board.create('tracecurve', [g1, p2]);
2523  *
2524  * </pre><div class="jxgbox" id="JXG5749fb7d-04fc-44d2-973e-45c1951e29ad" style="width: 300px; height: 300px;"></div>
2525  * <script type="text/javascript">
2526  *   var tc1_board = JXG.JSXGraph.initBoard('JXG5749fb7d-04fc-44d2-973e-45c1951e29ad', {boundingbox: [-4, 4, 4, -4], axis: false, showcopyright: false, shownavigation: false});
2527  *   var c1 = tc1_board.create('circle',[[0, 0], [2, 0]]),
2528  *       p1 = tc1_board.create('point',[-3, 1]),
2529  *       g1 = tc1_board.create('glider',[2, 1, c1]),
2530  *       s1 = tc1_board.create('segment',[g1, p1]),
2531  *       p2 = tc1_board.create('midpoint',[s1]),
2532  *       curve = tc1_board.create('tracecurve', [g1, p2]);
2533  * </script><pre>
2534  */
2535 JXG.createTracecurve = function (board, parents, attributes) {
2536     var c, glider, tracepoint, attr;
2537 
2538     if (parents.length !== 2) {
2539         throw new Error(
2540             "JSXGraph: Can't create trace curve with given parent'" +
2541             "\nPossible parent types: [glider, point]"
2542         );
2543     }
2544 
2545     glider = board.select(parents[0]);
2546     tracepoint = board.select(parents[1]);
2547 
2548     if (glider.type !== Const.OBJECT_TYPE_GLIDER || !Type.isPoint(tracepoint)) {
2549         throw new Error(
2550             "JSXGraph: Can't create trace curve with parent types '" +
2551             typeof parents[0] +
2552             "' and '" +
2553             typeof parents[1] +
2554             "'." +
2555             "\nPossible parent types: [glider, point]"
2556         );
2557     }
2558 
2559     attr = Type.copyAttributes(attributes, board.options, "tracecurve");
2560     attr.curvetype = "plot";
2561     c = board.create("curve", [[0], [0]], attr);
2562 
2563     /**
2564      * @class
2565      * @ignore
2566      */
2567     c.updateDataArray = function () {
2568         var i, step, t, el, pEl, x, y, from,
2569             savetrace,
2570             le = this.visProp.numberpoints,
2571             savePos = glider.position,
2572             slideObj = glider.slideObject,
2573             mi = slideObj.minX(),
2574             ma = slideObj.maxX();
2575 
2576         // set step width
2577         step = (ma - mi) / le;
2578         this.dataX = [];
2579         this.dataY = [];
2580 
2581         /*
2582          * For gliders on circles and lines a closed curve is computed.
2583          * For gliders on curves the curve is not closed.
2584          */
2585         if (slideObj.elementClass !== Const.OBJECT_CLASS_CURVE) {
2586             le++;
2587         }
2588 
2589         // Loop over all steps
2590         for (i = 0; i < le; i++) {
2591             t = mi + i * step;
2592             x = slideObj.X(t) / slideObj.Z(t);
2593             y = slideObj.Y(t) / slideObj.Z(t);
2594 
2595             // Position the glider
2596             glider.setPositionDirectly(Const.COORDS_BY_USER, [x, y]);
2597             from = false;
2598 
2599             // Update all elements from the glider up to the trace element
2600             for (el in this.board.objects) {
2601                 if (this.board.objects.hasOwnProperty(el)) {
2602                     pEl = this.board.objects[el];
2603 
2604                     if (pEl === glider) {
2605                         from = true;
2606                     }
2607 
2608                     if (from && pEl.needsRegularUpdate) {
2609                         // Save the trace mode of the element
2610                         savetrace = pEl.visProp.trace;
2611                         pEl.visProp.trace = false;
2612                         pEl.needsUpdate = true;
2613                         pEl.update(true);
2614 
2615                         // Restore the trace mode
2616                         pEl.visProp.trace = savetrace;
2617                         if (pEl === tracepoint) {
2618                             break;
2619                         }
2620                     }
2621                 }
2622             }
2623 
2624             // Store the position of the trace point
2625             this.dataX[i] = tracepoint.X();
2626             this.dataY[i] = tracepoint.Y();
2627         }
2628 
2629         // Restore the original position of the glider
2630         glider.position = savePos;
2631         from = false;
2632 
2633         // Update all elements from the glider to the trace point
2634         for (el in this.board.objects) {
2635             if (this.board.objects.hasOwnProperty(el)) {
2636                 pEl = this.board.objects[el];
2637                 if (pEl === glider) {
2638                     from = true;
2639                 }
2640 
2641                 if (from && pEl.needsRegularUpdate) {
2642                     savetrace = pEl.visProp.trace;
2643                     pEl.visProp.trace = false;
2644                     pEl.needsUpdate = true;
2645                     pEl.update(true);
2646                     pEl.visProp.trace = savetrace;
2647 
2648                     if (pEl === tracepoint) {
2649                         break;
2650                     }
2651                 }
2652             }
2653         }
2654     };
2655 
2656     return c;
2657 };
2658 
2659 JXG.registerElement("tracecurve", JXG.createTracecurve);
2660 
2661 /**
2662      * @class A step function is a function graph that is piecewise constant.
2663      *
2664      * In case the data points should be updated after creation time,
2665      * they can be accessed by curve.xterm and curve.yterm.
2666      * @pseudo
2667      * @name Stepfunction
2668      * @augments JXG.Curve
2669      * @constructor
2670      * @type Curve
2671      * @description JXG.Curve
2672      * @param {Array|Function} Parent1 elements of Stepfunction are two arrays containing the coordinates.
2673      * @param {Array|Function} Parent2
2674      * @see JXG.Curve
2675      * @example
2676      * // Create step function.
2677      var curve = board.create('stepfunction', [[0,1,2,3,4,5], [1,3,0,2,2,1]]);
2678 
2679      * </pre><div class="jxgbox" id="JXG32342ec9-ad17-4339-8a97-ff23dc34f51a" style="width: 300px; height: 300px;"></div>
2680      * <script type="text/javascript">
2681      *   var sf1_board = JXG.JSXGraph.initBoard('JXG32342ec9-ad17-4339-8a97-ff23dc34f51a', {boundingbox: [-1, 5, 6, -2], axis: true, showcopyright: false, shownavigation: false});
2682      *   var curve = sf1_board.create('stepfunction', [[0,1,2,3,4,5], [1,3,0,2,2,1]]);
2683      * </script><pre>
2684      */
2685 JXG.createStepfunction = function (board, parents, attributes) {
2686     var c, attr;
2687     if (parents.length !== 2) {
2688         throw new Error(
2689             "JSXGraph: Can't create step function with given parent'" +
2690             "\nPossible parent types: [array, array|function]"
2691         );
2692     }
2693 
2694     attr = Type.copyAttributes(attributes, board.options, "stepfunction");
2695     c = board.create("curve", parents, attr);
2696     /**
2697      * @class
2698      * @ignore
2699      */
2700     c.updateDataArray = function () {
2701         var i,
2702             j = 0,
2703             len = this.xterm.length;
2704 
2705         this.dataX = [];
2706         this.dataY = [];
2707 
2708         if (len === 0) {
2709             return;
2710         }
2711 
2712         this.dataX[j] = this.xterm[0];
2713         this.dataY[j] = this.yterm[0];
2714         ++j;
2715 
2716         for (i = 1; i < len; ++i) {
2717             this.dataX[j] = this.xterm[i];
2718             this.dataY[j] = this.dataY[j - 1];
2719             ++j;
2720             this.dataX[j] = this.xterm[i];
2721             this.dataY[j] = this.yterm[i];
2722             ++j;
2723         }
2724     };
2725 
2726     return c;
2727 };
2728 
2729 JXG.registerElement("stepfunction", JXG.createStepfunction);
2730 
2731 /**
2732  * @class A curve visualizing the function graph of the (numerical) derivative of a given curve.
2733  *
2734  * @pseudo
2735  * @name Derivative
2736  * @augments JXG.Curve
2737  * @constructor
2738  * @type JXG.Curve
2739  * @param {JXG.Curve} Parent Curve for which the derivative is generated.
2740  * @see JXG.Curve
2741  * @example
2742  * var cu = board.create('cardinalspline', [[[-3,0], [-1,2], [0,1], [2,0], [3,1]], 0.5, 'centripetal'], {createPoints: false});
2743  * var d = board.create('derivative', [cu], {dash: 2});
2744  *
2745  * </pre><div id="JXGb9600738-1656-11e8-8184-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
2746  * <script type="text/javascript">
2747  *     (function() {
2748  *         var board = JXG.JSXGraph.initBoard('JXGb9600738-1656-11e8-8184-901b0e1b8723',
2749  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2750  *     var cu = board.create('cardinalspline', [[[-3,0], [-1,2], [0,1], [2,0], [3,1]], 0.5, 'centripetal'], {createPoints: false});
2751  *     var d = board.create('derivative', [cu], {dash: 2});
2752  *
2753  *     })();
2754  *
2755  * </script><pre>
2756  *
2757  */
2758 JXG.createDerivative = function (board, parents, attributes) {
2759     var c, curve, dx, dy, attr;
2760 
2761     if (parents.length !== 1 && parents[0].class !== Const.OBJECT_CLASS_CURVE) {
2762         throw new Error(
2763             "JSXGraph: Can't create derivative curve with given parent'" +
2764             "\nPossible parent types: [curve]"
2765         );
2766     }
2767 
2768     attr = Type.copyAttributes(attributes, board.options, "curve");
2769 
2770     curve = parents[0];
2771     dx = Numerics.D(curve.X);
2772     dy = Numerics.D(curve.Y);
2773 
2774     c = board.create(
2775         "curve",
2776         [
2777             function (t) {
2778                 return curve.X(t);
2779             },
2780             function (t) {
2781                 return dy(t) / dx(t);
2782             },
2783             curve.minX(),
2784             curve.maxX()
2785         ],
2786         attr
2787     );
2788 
2789     c.setParents(curve);
2790 
2791     return c;
2792 };
2793 
2794 JXG.registerElement("derivative", JXG.createDerivative);
2795 
2796 /**
2797  * @class The path forming the intersection of two closed path elements.
2798  * The elements may be of type curve, circle, polygon, inequality.
2799  * If one element is a curve, it has to be closed.
2800  * The resulting element is of type curve.
2801  * @pseudo
2802  * @name CurveIntersection
2803  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element which is intersected
2804  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element which is intersected
2805  * @augments JXG.Curve
2806  * @constructor
2807  * @type JXG.Curve
2808  *
2809  * @example
2810  * var f = board.create('functiongraph', ['cos(x)']);
2811  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2812  * var circ = board.create('circle', [[0,0], 4]);
2813  * var clip = board.create('curveintersection', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2814  *
2815  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2816  * <script type="text/javascript">
2817  *     (function() {
2818  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2819  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2820  *     var f = board.create('functiongraph', ['cos(x)']);
2821  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2822  *     var circ = board.create('circle', [[0,0], 4]);
2823  *     var clip = board.create('curveintersection', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2824  *
2825  *     })();
2826  *
2827  * </script><pre>
2828  *
2829  */
2830 JXG.createCurveIntersection = function (board, parents, attributes) {
2831     var c;
2832 
2833     if (parents.length !== 2) {
2834         throw new Error(
2835             "JSXGraph: Can't create curve intersection with given parent'" +
2836             "\nPossible parent types: [array, array|function]"
2837         );
2838     }
2839 
2840     c = board.create("curve", [[], []], attributes);
2841     /**
2842      * @class
2843      * @ignore
2844      */
2845     c.updateDataArray = function () {
2846         var a = Clip.intersection(parents[0], parents[1], this.board);
2847         this.dataX = a[0];
2848         this.dataY = a[1];
2849     };
2850     return c;
2851 };
2852 
2853 /**
2854  * @class The path forming the union of two closed path elements.
2855  * The elements may be of type curve, circle, polygon, inequality.
2856  * If one element is a curve, it has to be closed.
2857  * The resulting element is of type curve.
2858  * @pseudo
2859  * @name CurveUnion
2860  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element defining the union
2861  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element defining the union
2862  * @augments JXG.Curve
2863  * @constructor
2864  * @type JXG.Curve
2865  *
2866  * @example
2867  * var f = board.create('functiongraph', ['cos(x)']);
2868  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2869  * var circ = board.create('circle', [[0,0], 4]);
2870  * var clip = board.create('curveunion', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2871  *
2872  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2873  * <script type="text/javascript">
2874  *     (function() {
2875  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2876  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2877  *     var f = board.create('functiongraph', ['cos(x)']);
2878  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2879  *     var circ = board.create('circle', [[0,0], 4]);
2880  *     var clip = board.create('curveunion', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2881  *
2882  *     })();
2883  *
2884  * </script><pre>
2885  *
2886  */
2887 JXG.createCurveUnion = function (board, parents, attributes) {
2888     var c;
2889 
2890     if (parents.length !== 2) {
2891         throw new Error(
2892             "JSXGraph: Can't create curve union with given parent'" +
2893             "\nPossible parent types: [array, array|function]"
2894         );
2895     }
2896 
2897     c = board.create("curve", [[], []], attributes);
2898     /**
2899      * @class
2900      * @ignore
2901      */
2902     c.updateDataArray = function () {
2903         var a = Clip.union(parents[0], parents[1], this.board);
2904         this.dataX = a[0];
2905         this.dataY = a[1];
2906     };
2907     return c;
2908 };
2909 
2910 /**
2911  * @class The path forming the difference of two closed path elements.
2912  * The elements may be of type curve, circle, polygon, inequality.
2913  * If one element is a curve, it has to be closed.
2914  * The resulting element is of type curve.
2915  * @pseudo
2916  * @name CurveDifference
2917  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element from which the second element is "subtracted"
2918  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element which is subtracted from the first element
2919  * @augments JXG.Curve
2920  * @constructor
2921  * @type JXG.Curve
2922  *
2923  * @example
2924  * var f = board.create('functiongraph', ['cos(x)']);
2925  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2926  * var circ = board.create('circle', [[0,0], 4]);
2927  * var clip = board.create('curvedifference', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2928  *
2929  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2930  * <script type="text/javascript">
2931  *     (function() {
2932  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2933  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2934  *     var f = board.create('functiongraph', ['cos(x)']);
2935  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2936  *     var circ = board.create('circle', [[0,0], 4]);
2937  *     var clip = board.create('curvedifference', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2938  *
2939  *     })();
2940  *
2941  * </script><pre>
2942  *
2943  */
2944 JXG.createCurveDifference = function (board, parents, attributes) {
2945     var c;
2946 
2947     if (parents.length !== 2) {
2948         throw new Error(
2949             "JSXGraph: Can't create curve difference with given parent'" +
2950             "\nPossible parent types: [array, array|function]"
2951         );
2952     }
2953 
2954     c = board.create("curve", [[], []], attributes);
2955     /**
2956      * @class
2957      * @ignore
2958      */
2959     c.updateDataArray = function () {
2960         var a = Clip.difference(parents[0], parents[1], this.board);
2961         this.dataX = a[0];
2962         this.dataY = a[1];
2963     };
2964     return c;
2965 };
2966 
2967 JXG.registerElement("curvedifference", JXG.createCurveDifference);
2968 JXG.registerElement("curveintersection", JXG.createCurveIntersection);
2969 JXG.registerElement("curveunion", JXG.createCurveUnion);
2970 
2971 // /**
2972 //  * @class Concat of two path elements, in general neither is a closed path. The parent elements have to be curves, too.
2973 //  * The resulting element is of type curve. The curve points are simply concatenated.
2974 //  * @pseudo
2975 //  * @name CurveConcat
2976 //  * @param {JXG.Curve} curve1 First curve element.
2977 //  * @param {JXG.Curve} curve2 Second curve element.
2978 //  * @augments JXG.Curve
2979 //  * @constructor
2980 //  * @type JXG.Curve
2981 //  */
2982 // JXG.createCurveConcat = function (board, parents, attributes) {
2983 //     var c;
2984 
2985 //     if (parents.length !== 2) {
2986 //         throw new Error(
2987 //             "JSXGraph: Can't create curve difference with given parent'" +
2988 //                 "\nPossible parent types: [array, array|function]"
2989 //         );
2990 //     }
2991 
2992 //     c = board.create("curve", [[], []], attributes);
2993 //     /**
2994 //      * @class
2995 //      * @ignore
2996 //      */
2997 //     c.updateCurve = function () {
2998 //         this.points = parents[0].points.concat(
2999 //                 [new JXG.Coords(Const.COORDS_BY_USER, [NaN, NaN], this.board)]
3000 //             ).concat(parents[1].points);
3001 //         this.numberPoints = this.points.length;
3002 //         return this;
3003 //     };
3004 
3005 //     return c;
3006 // };
3007 
3008 // JXG.registerElement("curveconcat", JXG.createCurveConcat);
3009 
3010 /**
3011  * @class Vertical or horizontal box plot curve to present numerical data through their quartiles.
3012  * The direction of the box plot is controlled by the attribute "dir".
3013  * @pseudo
3014  * @name Boxplot
3015  * @param {Array} quantiles Array containing at least five quantiles. The elements can be of type number, function or string.
3016  * @param {Number|Function} axis Axis position of the box plot
3017  * @param {Number|Function} width Width of the rectangle part of the box plot. The width of the first and 4th quantile
3018  * is relative to this width and can be controlled by the attribute "smallWidth".
3019  * @augments JXG.Curve
3020  * @constructor
3021  * @type JXG.Curve
3022  *
3023  * @example
3024  * var Q = [ -1, 2, 3, 3.5, 5 ];
3025  *
3026  * var b = board.create('boxplot', [Q, 2, 4], {strokeWidth: 3});
3027  *
3028  * </pre><div id="JXG13eb23a1-a641-41a2-be11-8e03e400a947" class="jxgbox" style="width: 300px; height: 300px;"></div>
3029  * <script type="text/javascript">
3030  *     (function() {
3031  *         var board = JXG.JSXGraph.initBoard('JXG13eb23a1-a641-41a2-be11-8e03e400a947',
3032  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3033  *     var Q = [ -1, 2, 3, 3.5, 5 ];
3034  *     var b = board.create('boxplot', [Q, 2, 4], {strokeWidth: 3});
3035  *
3036  *     })();
3037  *
3038  * </script><pre>
3039  *
3040  * @example
3041  * var Q = [ -1, 2, 3, 3.5, 5 ];
3042  * var b = board.create('boxplot', [Q, 3, 4], {dir: 'horizontal', smallWidth: 0.25, color:'red'});
3043  *
3044  * </pre><div id="JXG0deb9cb2-84bc-470d-a6db-8be9a5694813" class="jxgbox" style="width: 300px; height: 300px;"></div>
3045  * <script type="text/javascript">
3046  *     (function() {
3047  *         var board = JXG.JSXGraph.initBoard('JXG0deb9cb2-84bc-470d-a6db-8be9a5694813',
3048  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3049  *     var Q = [ -1, 2, 3, 3.5, 5 ];
3050  *     var b = board.create('boxplot', [Q, 3, 4], {dir: 'horizontal', smallWidth: 0.25, color:'red'});
3051  *
3052  *     })();
3053  *
3054  * </script><pre>
3055  *
3056  * @example
3057  * var data = [57, 57, 57, 58, 63, 66, 66, 67, 67, 68, 69, 70, 70, 70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81];
3058  * var Q = [];
3059  *
3060  * Q[0] = JXG.Math.Statistics.min(data);
3061  * Q = Q.concat(JXG.Math.Statistics.percentile(data, [25, 50, 75]));
3062  * Q[4] = JXG.Math.Statistics.max(data);
3063  *
3064  * var b = board.create('boxplot', [Q, 0, 3]);
3065  *
3066  * </pre><div id="JXGef079e76-ae99-41e4-af29-1d07d83bf85a" class="jxgbox" style="width: 300px; height: 300px;"></div>
3067  * <script type="text/javascript">
3068  *     (function() {
3069  *         var board = JXG.JSXGraph.initBoard('JXGef079e76-ae99-41e4-af29-1d07d83bf85a',
3070  *             {boundingbox: [-5,90,5,30], axis: true, showcopyright: false, shownavigation: false});
3071  *     var data = [57, 57, 57, 58, 63, 66, 66, 67, 67, 68, 69, 70, 70, 70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81];
3072  *     var Q = [];
3073  *
3074  *     Q[0] = JXG.Math.Statistics.min(data);
3075  *     Q = Q.concat(JXG.Math.Statistics.percentile(data, [25, 50, 75]));
3076  *     Q[4] = JXG.Math.Statistics.max(data);
3077  *
3078  *     var b = board.create('boxplot', [Q, 0, 3]);
3079  *
3080  *     })();
3081  *
3082  * </script><pre>
3083  *
3084  * @example
3085  * var mi = board.create('glider', [0, -1, board.defaultAxes.y]);
3086  * var ma = board.create('glider', [0, 5, board.defaultAxes.y]);
3087  * var Q = [function() { return mi.Y(); }, 2, 3, 3.5, function() { return ma.Y(); }];
3088  *
3089  * var b = board.create('boxplot', [Q, 0, 2]);
3090  *
3091  * </pre><div id="JXG3b3225da-52f0-42fe-8396-be9016bf289b" class="jxgbox" style="width: 300px; height: 300px;"></div>
3092  * <script type="text/javascript">
3093  *     (function() {
3094  *         var board = JXG.JSXGraph.initBoard('JXG3b3225da-52f0-42fe-8396-be9016bf289b',
3095  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3096  *     var mi = board.create('glider', [0, -1, board.defaultAxes.y]);
3097  *     var ma = board.create('glider', [0, 5, board.defaultAxes.y]);
3098  *     var Q = [function() { return mi.Y(); }, 2, 3, 3.5, function() { return ma.Y(); }];
3099  *
3100  *     var b = board.create('boxplot', [Q, 0, 2]);
3101  *
3102  *     })();
3103  *
3104  * </script><pre>
3105  *
3106  */
3107 JXG.createBoxPlot = function (board, parents, attributes) {
3108     var box, i, len,
3109         attr = Type.copyAttributes(attributes, board.options, "boxplot");
3110 
3111     if (parents.length !== 3) {
3112         throw new Error(
3113             "JSXGraph: Can't create box plot with given parent'" +
3114             "\nPossible parent types: [array, number|function, number|function] containing quantiles, axis, width"
3115         );
3116     }
3117     if (parents[0].length < 5) {
3118         throw new Error(
3119             "JSXGraph: Can't create box plot with given parent[0]'" +
3120             "\nparent[0] has to contain at least 5 quantiles."
3121         );
3122     }
3123     box = board.create("curve", [[], []], attr);
3124 
3125     len = parents[0].length; // Quantiles
3126     box.Q = [];
3127     for (i = 0; i < len; i++) {
3128         box.Q[i] = Type.createFunction(parents[0][i], board);
3129     }
3130     box.x = Type.createFunction(parents[1], board);
3131     box.w = Type.createFunction(parents[2], board);
3132 
3133     /**
3134      * @class
3135      * @ignore
3136      */
3137     box.updateDataArray = function () {
3138         var v1, v2, l1, l2, r1, r2, w2, dir, x;
3139 
3140         w2 = this.evalVisProp('smallwidth');
3141         dir = this.evalVisProp('dir');
3142         x = this.x();
3143         l1 = x - this.w() * 0.5;
3144         l2 = x - this.w() * 0.5 * w2;
3145         r1 = x + this.w() * 0.5;
3146         r2 = x + this.w() * 0.5 * w2;
3147         v1 = [x, l2, r2, x, x, l1, l1, r1, r1, x, NaN, l1, r1, NaN, x, x, l2, r2, x];
3148         v2 = [
3149             this.Q[0](),
3150             this.Q[0](),
3151             this.Q[0](),
3152             this.Q[0](),
3153             this.Q[1](),
3154             this.Q[1](),
3155             this.Q[3](),
3156             this.Q[3](),
3157             this.Q[1](),
3158             this.Q[1](),
3159             NaN,
3160             this.Q[2](),
3161             this.Q[2](),
3162             NaN,
3163             this.Q[3](),
3164             this.Q[4](),
3165             this.Q[4](),
3166             this.Q[4](),
3167             this.Q[4]()
3168         ];
3169         if (dir === "vertical") {
3170             this.dataX = v1;
3171             this.dataY = v2;
3172         } else {
3173             this.dataX = v2;
3174             this.dataY = v1;
3175         }
3176     };
3177 
3178     box.addParentsFromJCFunctions([box.Q, box.x, box.w]);
3179 
3180     return box;
3181 };
3182 
3183 JXG.registerElement("boxplot", JXG.createBoxPlot);
3184 
3185 /**
3186  * @class An implicit curve is a plane curve defined by an implicit equation
3187  * relating two coordinate variables, commonly <i>x</i> and <i>y</i>.
3188  * For example, the unit circle is defined by the implicit equation
3189  * x<sup>2</sup> + y<sup>2</sup> = 1.
3190  * In general, every implicit curve is defined by an equation of the form
3191  * <i>f(x, y) = 0</i>
3192  * for some function <i>f</i> of two variables. (<a href="https://en.wikipedia.org/wiki/Implicit_curve">Wikipedia</a>)
3193  * <p>
3194  * The partial derivatives for <i>f</i> are optional. If not given, numerical
3195  * derivatives are used instead. This is good enough for most practical use cases.
3196  * But if supplied, both partial derivatives must be supplied.
3197  * <p>
3198  * The most effective attributes to tinker with if the implicit curve algorithm fails are
3199  * {@link ImplicitCurve#resolution_outer},
3200  * {@link ImplicitCurve#resolution_inner},
3201  * {@link ImplicitCurve#alpha_0},
3202  * {@link ImplicitCurve#h_initial},
3203  * {@link ImplicitCurve#h_max}, and
3204  * {@link ImplicitCurve#qdt_box}.
3205  *
3206  * @pseudo
3207  * @name ImplicitCurve
3208  * @param {Function|String} f Function of two variables for the left side of the equation <i>f(x,y)=0</i>.
3209  * If f is supplied as string, it has to use the variables 'x' and 'y'.
3210  * @param {Function|String} [dfx=null] Optional partial derivative in respect to the first variable
3211  * If dfx is supplied as string, it has to use the variables 'x' and 'y'.
3212  * @param {Function|String} [dfy=null] Optional partial derivative in respect to the second variable
3213  * If dfy is supplied as string, it has to use the variables 'x' and 'y'.
3214  * @param {Array|Function} [rangex=boundingbox] Optional array of length 2
3215  * of the form [x_min, x_max] setting the domain of the x coordinate of the implicit curve.
3216  * If not supplied, the board's boundingbox (+ the attribute "margin") is taken.
3217  * For algorithmic reasons, the plotted curve mighty slightly overflow the given domain.
3218  * @param {Array|Function} [rangey=boundingbox] Optional array of length 2
3219  * of the form [y_min, y_max] setting the domain of the y coordinate of the implicit curve.
3220  * If not supplied, the board's boundingbox (+ the attribute "margin") is taken.
3221  * For algorithmic reasons, the plotted curve mighty slightly overflow the given domain.
3222  * @augments JXG.Curve
3223  * @constructor
3224  * @type JXG.Curve
3225  *
3226  * @example
3227  *   var f, c;
3228  *   f = (x, y) => 1 / 16 * x ** 2 + y ** 2 - 1;
3229  *   c = board.create('implicitcurve', [f], {
3230  *       strokeWidth: 3,
3231  *       strokeColor: JXG.palette.red,
3232  *       strokeOpacity: 0.8
3233  *   });
3234  *
3235  * </pre><div id="JXGa6e86701-1a82-48d0-b007-3a3d32075076" class="jxgbox" style="width: 300px; height: 300px;"></div>
3236  * <script type="text/javascript">
3237  *     (function() {
3238  *         var board = JXG.JSXGraph.initBoard('JXGa6e86701-1a82-48d0-b007-3a3d32075076',
3239  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3240  *             var f, c;
3241  *             f = (x, y) => 1 / 16 * x ** 2 + y ** 2 - 1;
3242  *             c = board.create('implicitcurve', [f], {
3243  *                 strokeWidth: 3,
3244  *                 strokeColor: JXG.palette.red,
3245  *                 strokeOpacity: 0.8
3246  *             });
3247  *
3248  *     })();
3249  *
3250  * </script><pre>
3251  *
3252  * @example
3253  *  var a, c, f;
3254  *  a = board.create('slider', [[-3, 6], [3, 6], [-3, 1, 3]], {
3255  *      name: 'a', stepWidth: 0.1
3256  *  });
3257  *  f = (x, y) => x ** 2 - 2 * x * y - 2 * x + (a.Value() + 1) * y ** 2 + (4 * a.Value() + 2) * y + 4 * a.Value() - 3;
3258  *  c = board.create('implicitcurve', [f], {
3259  *      strokeWidth: 3,
3260  *      strokeColor: JXG.palette.red,
3261  *      strokeOpacity: 0.8,
3262  *      resolution_outer: 20,
3263  *      resolution_inner: 20
3264  *  });
3265  *
3266  * </pre><div id="JXG0b133a54-9509-4a65-9722-9c5145e23b40" class="jxgbox" style="width: 300px; height: 300px;"></div>
3267  * <script type="text/javascript">
3268  *     (function() {
3269  *         var board = JXG.JSXGraph.initBoard('JXG0b133a54-9509-4a65-9722-9c5145e23b40',
3270  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3271  *             var a, c, f;
3272  *             a = board.create('slider', [[-3, 6], [3, 6], [-3, 1, 3]], {
3273  *                 name: 'a', stepWidth: 0.1
3274  *             });
3275  *             f = (x, y) => x ** 2 - 2 * x * y - 2 * x + (a.Value() + 1) * y ** 2 + (4 * a.Value() + 2) * y + 4 * a.Value() - 3;
3276  *             c = board.create('implicitcurve', [f], {
3277  *                 strokeWidth: 3,
3278  *                 strokeColor: JXG.palette.red,
3279  *                 strokeOpacity: 0.8,
3280  *                 resolution_outer: 20,
3281  *                 resolution_inner: 20
3282  *             });
3283  *
3284  *     })();
3285  *
3286  * </script><pre>
3287  *
3288  * @example
3289  *  var c = board.create('implicitcurve', ['abs(x * y) - 3'], {
3290  *      strokeWidth: 3,
3291  *      strokeColor: JXG.palette.red,
3292  *      strokeOpacity: 0.8
3293  *  });
3294  *
3295  * </pre><div id="JXG02802981-0abb-446b-86ea-ee588f02ed1a" class="jxgbox" style="width: 300px; height: 300px;"></div>
3296  * <script type="text/javascript">
3297  *     (function() {
3298  *         var board = JXG.JSXGraph.initBoard('JXG02802981-0abb-446b-86ea-ee588f02ed1a',
3299  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3300  *             var c = board.create('implicitcurve', ['abs(x * y) - 3'], {
3301  *                 strokeWidth: 3,
3302  *                 strokeColor: JXG.palette.red,
3303  *                 strokeOpacity: 0.8
3304  *             });
3305  *
3306  *     })();
3307  *
3308  * </script><pre>
3309  *
3310  * @example
3311  * var niveauline = [];
3312  * niveauline = [0.5, 1, 1.5, 2];
3313  * for (let i = 0; i < niveauline.length; i++) {
3314  *     board.create("implicitcurve", [
3315  *         (x, y) => x ** .5 * y ** .5 - niveauline[i],
3316            [0.25, 3], [0.5, 4] // Domain
3317  *     ], {
3318  *         strokeWidth: 2,
3319  *         strokeColor: JXG.palette.red,
3320  *         strokeOpacity: (1 + i) / niveauline.length,
3321  *         needsRegularUpdate: false
3322  *     });
3323  * }
3324  *
3325  * </pre><div id="JXGccee9aab-6dd9-4a79-827d-3164f70cc6a1" class="jxgbox" style="width: 300px; height: 300px;"></div>
3326  * <script type="text/javascript">
3327  *     (function() {
3328  *         var board = JXG.JSXGraph.initBoard('JXGccee9aab-6dd9-4a79-827d-3164f70cc6a1',
3329  *             {boundingbox: [-1, 5, 5,-1], axis: true, showcopyright: false, shownavigation: false});
3330  *         var niveauline = [];
3331  *         niveauline = [0.5, 1, 1.5, 2];
3332  *         for (let i = 0; i < niveauline.length; i++) {
3333  *             board.create("implicitcurve", [
3334  *                 (x, y) => x ** .5 * y ** .5 - niveauline[i],
3335  *                 [0.25, 3], [0.5, 4]
3336  *             ], {
3337  *                 strokeWidth: 2,
3338  *                 strokeColor: JXG.palette.red,
3339  *                 strokeOpacity: (1 + i) / niveauline.length,
3340  *                 needsRegularUpdate: false
3341  *             });
3342  *         }
3343  *
3344  *     })();
3345  *
3346  * </script><pre>
3347  *
3348  */
3349 JXG.createImplicitCurve = function (board, parents, attributes) {
3350     var c, attr;
3351 
3352     if ([1, 3, 5].indexOf(parents.length) < 0) {
3353         throw new Error(
3354             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3355             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3356             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3357         );
3358     }
3359 
3360     // if (parents.length === 3) {
3361     //     if (!Type.isArray(parents[1]) && !Type.isArray(parents[2])) {
3362     //         throw new Error(
3363     //             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3364     //             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3365     //             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3366     //         );
3367     //     }
3368     // }
3369     // if (parents.length === 5) {
3370     //     if (!Type.isArray(parents[3]) && !Type.isArray(parents[4])) {
3371     //         throw new Error(
3372     //             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3373     //             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3374     //             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3375     //         );
3376     //     }
3377     // }
3378 
3379     attr = Type.copyAttributes(attributes, board.options, "implicitcurve");
3380     c = board.create("curve", [[], []], attr);
3381 
3382     /**
3383      * Function of two variables for the left side of the equation <i>f(x,y)=0</i>.
3384      *
3385      * @name f
3386      * @memberOf ImplicitCurve.prototype
3387      * @function
3388      * @returns {Number}
3389      */
3390     c.f = Type.createFunction(parents[0], board, 'x, y');
3391 
3392     /**
3393      * Partial derivative in the first variable of
3394      * the left side of the equation <i>f(x,y)=0</i>.
3395      * If null, then numerical derivative is used.
3396      *
3397      * @name dfx
3398      * @memberOf ImplicitCurve.prototype
3399      * @function
3400      * @returns {Number}
3401      */
3402     if (parents.length === 5 || Type.isString(parents[1]) || Type.isFunction(parents[1])) {
3403         c.dfx = Type.createFunction(parents[1], board, 'x, y');
3404     } else {
3405         c.dfx = null;
3406     }
3407 
3408     /**
3409      * Partial derivative in the second variable of
3410      * the left side of the equation <i>f(x,y)=0</i>.
3411      * If null, then numerical derivative is used.
3412      *
3413      * @name dfy
3414      * @memberOf ImplicitCurve.prototype
3415      * @function
3416      * @returns {Number}
3417      */
3418     if (parents.length === 5 || Type.isString(parents[2]) || Type.isFunction(parents[2])) {
3419         c.dfy = Type.createFunction(parents[2], board, 'x, y');
3420     } else {
3421         c.dfy = null;
3422     }
3423 
3424     /**
3425      * Defines a domain for searching f(x,y)=0. Default is null, meaning
3426      * the bounding box of the board is used.
3427      * Using domain, visProp.margin is ignored.
3428      * @name domain
3429      * @memberOf ImplicitCurve.prototype
3430      * @param {Array} of length 4 defining the domain used to compute the implict curve.
3431      * Syntax: [x_min, y_max, x_max, y_min]
3432      */
3433     // c.domain = board.getBoundingBox();
3434     c.domain = null;
3435     if (parents.length === 5) {
3436         c.domain = [parents[3], parents[4]];
3437         // c.visProp.margin = 0;
3438     } else if (parents.length === 3) {
3439         c.domain = [parents[1], parents[2]];
3440         // c.visProp.margin = 0;
3441     }
3442 
3443     /**
3444      * @class
3445      * @ignore
3446      */
3447     c.updateDataArray = function () {
3448         var bbox, rx, ry,
3449             ip, cfg,
3450             ret = [],
3451             mgn;
3452 
3453         if (this.domain === null) {
3454             mgn = this.evalVisProp('margin');
3455             bbox = this.board.getBoundingBox();
3456             bbox[0] -= mgn;
3457             bbox[1] += mgn;
3458             bbox[2] += mgn;
3459             bbox[3] -= mgn;
3460         } else {
3461             rx = Type.evaluate(this.domain[0]);
3462             ry = Type.evaluate(this.domain[1]);
3463             bbox = [rx[0], ry[1], rx[1], ry[0]];
3464         }
3465 
3466         cfg = {
3467             resolution_out: Math.max(0.01, this.evalVisProp('resolution_outer')),
3468             resolution_in: Math.max(0.01, this.evalVisProp('resolution_inner')),
3469             max_steps: this.evalVisProp('max_steps'),
3470             alpha_0: this.evalVisProp('alpha_0'),
3471             tol_u0: this.evalVisProp('tol_u0'),
3472             tol_newton: this.evalVisProp('tol_newton'),
3473             tol_cusp: this.evalVisProp('tol_cusp'),
3474             tol_progress: this.evalVisProp('tol_progress'),
3475             qdt_box: this.evalVisProp('qdt_box'),
3476             kappa_0: this.evalVisProp('kappa_0'),
3477             delta_0: this.evalVisProp('delta_0'),
3478             h_initial: this.evalVisProp('h_initial'),
3479             h_critical: this.evalVisProp('h_critical'),
3480             h_max: this.evalVisProp('h_max'),
3481             loop_dist: this.evalVisProp('loop_dist'),
3482             loop_dir: this.evalVisProp('loop_dir'),
3483             loop_detection: this.evalVisProp('loop_detection'),
3484             unitX: this.board.unitX,
3485             unitY: this.board.unitY
3486         };
3487         this.dataX = [];
3488         this.dataY = [];
3489 
3490         // console.time("implicit plot");
3491         ip = new ImplicitPlot(bbox, cfg, this.f, this.dfx, this.dfy);
3492         this.qdt = ip.qdt;
3493 
3494         ret = ip.plot();
3495         // console.timeEnd("implicit plot");
3496 
3497         this.dataX = ret[0];
3498         this.dataY = ret[1];
3499     };
3500 
3501     c.elType = 'implicitcurve';
3502 
3503     return c;
3504 };
3505 
3506 JXG.registerElement("implicitcurve", JXG.createImplicitCurve);
3507 
3508 
3509 export default JXG.Curve;
3510 
3511 // export default {
3512 //     Curve: JXG.Curve,
3513 //     createCardinalSpline: JXG.createCardinalSpline,
3514 //     createCurve: JXG.createCurve,
3515 //     createCurveDifference: JXG.createCurveDifference,
3516 //     createCurveIntersection: JXG.createCurveIntersection,
3517 //     createCurveUnion: JXG.createCurveUnion,
3518 //     createDerivative: JXG.createDerivative,
3519 //     createFunctiongraph: JXG.createFunctiongraph,
3520 //     createMetapostSpline: JXG.createMetapostSpline,
3521 //     createPlot: JXG.createFunctiongraph,
3522 //     createSpline: JXG.createSpline,
3523 //     createRiemannsum: JXG.createRiemannsum,
3524 //     createStepfunction: JXG.createStepfunction,
3525 //     createTracecurve: JXG.createTracecurve
3526 // };
3527 
3528 // const Curve = JXG.Curve;
3529 // export { Curve as default, Curve};
3530