Difference between revisions of "Change Equation of a Graph"

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This example shows how you can change the equation of a graph without creating the whole construction again.
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This example shows how you can change the equation of a graph without creating the whole construction again. Dependent elements are updated automatically.
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<html><br />
 +
<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">
 +
<input type="button" value="set" onClick="doIt()" style='margin:1em'>
 +
</html>
 +
<jsxgraph width="600" height="400" box="jxgbox">
 +
var board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-6, 12, 8, -6], axis: true});
 +
 +
eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
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var graph = board.create('functiongraph', [function(x){ return f(x); }, -10, 10]),
 +
    p1 = board.create('glider', [0,0,graph], {style:6, name:'P'}),
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    p2 = board.create('point', [function() { return p1.X()+1;}, function() {return p1.Y()+JXG.Math.Numerics.D(graph.Y)(p1.X());}], {style:1, name:''}),
 +
    l1 = board.create('line', [p1,p2],{}),
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    p3 = board.create('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''}),
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    pol = board.create('polygon', [p1,p2,p3], {}),
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    t = board.create('text', [function(){return p1.X()+1.1;},function(){return p1.Y()+(p2.Y()-p3.Y())/2;},function(){ return "m="+((p2.Y()-p3.Y()).toFixed(2));}]);
 +
           
 +
    function doIt(){
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        eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
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        graph.Y = function(x){ return f(x); };
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        graph.updateCurve();
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        board.update();
 +
    }
 +
</jsxgraph>
 +
 
 +
 
 +
== How to Create this Construction ==
 +
 
 +
=== HTML Part ===
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'''Adding a text input field somewhere on the page together with a button'''
  
<div style="width:960px">
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<source lang="xml">
<div id="jxgbox" class="jxgbox" style="width:600px; height:400px; float:left; "></div>
 
<p style="float:right">
 
 
<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">
 
<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">
 +
<input type="button" value="set" onClick="doIt()">
 +
</source>
  
<input type="button" value="set" onClick="doIt()" style='margin:1em'>
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=== JavaScript Part ===
</p>
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Setting up the board
</div>
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<source lang="javascript">
<br clear=all>
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board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-6, 12, 8, -6], axis: true});
<div id="debug" style="display:none;"></div>
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</source>
  <script type="text/javascript">
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    /* <![CDATA[ */
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Create a JavaScript Function f(x) From the Text Field
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<source lang="javascript">
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eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
 +
</source>
 +
 
 +
Use f(x) for defining the Graph
 +
<source lang="javascript">
 +
graph = board.create('functiongraph', [function(x){ return f(x); },-10, 10]);
 +
</source>
 +
 
 +
The slope triangle
 +
<source lang="javascript">
 +
//glider on the curve
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p1 = board.create('glider', [0,0,graph], {style:6, name:'P'});
 +
//define the derivative of f
 +
g = JXG.Math.Numerics.D(f);
 +
//a point on the tangent
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//                                variable x coordinate          variable y coordinate depending on the derivative of f at point p1.X()
 +
p2 = board.create('point', [function() { return p1.X()+1;}, function() {return p1.Y()+JXG.Math.Numerics.D(graph.Y)(p1.X());}], {style:1, name:''});
 +
//the tangent
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l1 = board.create('line', [p1,p2],{});
 +
//a third point fpr the slope triangle
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p3 = board.create('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''});
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//the slope triangle
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pol = board.create('polygon', [p1,p2,p3], {});
 +
//a text for displaying slope's value
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//                              variable x coordinate          variable y coordinate                        variable value
 +
t = board.create('text', [function(){return p1.X()+1.1;},function(){return p1.Y()+(p2.Y()-p3.Y())/2;},function(){ return "m="+(p2.Y()-p3.Y()).toFixed(2);}],{color:ff0000});  
 +
</source>
 +
 
 +
Change the plotted function
 +
<source lang="javascript">
 +
function doIt(){
 +
  //redefine function f according to the current text field value
 +
  eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
 +
  //change the Y attribute of the graph to the new function
 +
  graph.Y = function(x){ return f(x); };
 +
  //update the graph
 +
  graph.updateCurve();
 +
  //update the whole board
 +
  board.update();
 +
}
 +
</source>
 +
 
 +
== Remarks ==
 +
The doIt() function is only responsible for updating the graph. All other dependend objects are self-updating, especially the object p2 which depends on the derivative of function f. This is all done by anonymous functions of JavaScript.
  
        board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
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[[Category:Examples]]
// Axes
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[[Category:Calculus]]
        b1axisx = board.createElement('axis', [[1,0], [0,0]], {});
 
        b1axisy = board.createElement('axis', [[0,1], [0,0]], {});
 
 
eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
 
graph = board.createElement('curve', [function(x){ return x; }, function(x){ return f(x); }, "x", -10, 10]);
 
//graph = eval("board.createElement('curve', [function(x){ return x; }, function(x){ return "+document.getElementById("eingabe").value+";}, 'x', -10, 10])");
 
//graph.curveType = "graph";
 
        p1 = board.createElement('glider', [graph], {style:6, name:'P'});
 
        g = board.algebra.D(f);
 
        p2 = board.createElement('point', [function() { return p1.X()+1;}, function() {return p1.Y()+board.algebra.D(graph.Y)(p1.X());}], {style:1, name:''});
 
        l1 = board.createElement('line', [p1,p2],{});
 
        p3 = board.createElement('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''});
 
        pol = board.createElement('polygon', [p1,p2,p3], {});
 
        t = board.createElement('text', [function(){return p1.X()+1.1;},function(){return p1.Y()+(p2.Y()-p3.Y())/2;},function(){ return "m="+(board.round(p2.Y()-p3.Y(),2));}]);
 
           
 
       
 
        function doIt(){
 
        eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
 
        graph.yterm = function(x){ return f(x); };  // usually: e.g. "x^2"
 
//graph.yterm = eval("function(x){ return "+document.getElementById("eingabe").value+"; };");
 
    graph.Y = graph.yterm;
 
    graph.updateCurve();
 
    board.update();
 
        }
 
       
 
  /* ]]> */
 
  </script>
 

Latest revision as of 10:30, 3 April 2019

This example shows how you can change the equation of a graph without creating the whole construction again. Dependent elements are updated automatically.


How to Create this Construction

HTML Part

Adding a text input field somewhere on the page together with a button

<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">
<input type="button" value="set" onClick="doIt()">

JavaScript Part

Setting up the board

board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-6, 12, 8, -6], axis: true});

Create a JavaScript Function f(x) From the Text Field

eval("function f(x){ return "+document.getElementById("eingabe").value+";}");

Use f(x) for defining the Graph

graph = board.create('functiongraph', [function(x){ return f(x); },-10, 10]);

The slope triangle

//glider on the curve
p1 = board.create('glider', [0,0,graph], {style:6, name:'P'});
//define the derivative of f
g = JXG.Math.Numerics.D(f);
//a point on the tangent
//                                 variable x coordinate           variable y coordinate depending on the derivative of f at point p1.X()
p2 = board.create('point', [function() { return p1.X()+1;}, function() {return p1.Y()+JXG.Math.Numerics.D(graph.Y)(p1.X());}], {style:1, name:''});
//the tangent 
l1 = board.create('line', [p1,p2],{}); 
//a third point fpr the slope triangle
p3 = board.create('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''});
//the slope triangle
pol = board.create('polygon', [p1,p2,p3], {});
//a text for displaying slope's value
//                               variable x coordinate          variable y coordinate                        variable value
t = board.create('text', [function(){return p1.X()+1.1;},function(){return p1.Y()+(p2.Y()-p3.Y())/2;},function(){ return "m="+(p2.Y()-p3.Y()).toFixed(2);}],{color:ff0000});

Change the plotted function

function doIt(){
  //redefine function f according to the current text field value
  eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
  //change the Y attribute of the graph to the new function 
  graph.Y = function(x){ return f(x); };
  //update the graph
  graph.updateCurve();
  //update the whole board
  board.update();
}

Remarks

The doIt() function is only responsible for updating the graph. All other dependend objects are self-updating, especially the object p2 which depends on the derivative of function f. This is all done by anonymous functions of JavaScript.