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. Dependend elements are updated automatically.
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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.
<html>
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<html><br />
<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
 
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
 
<div style="width:960px">
 
<div id="jxgbox" class="jxgbox" style="width:600px; height:400px;"></div>
 
<p>
 
 
<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()" style='margin:1em'>  
 
<input type="button" value="set" onClick="doIt()" style='margin:1em'>  
</p>
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</html>
</div>
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<jsxgraph width="600" height="400" box="jxgbox">
<div id="debug" style="display:none;"></div>
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var board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-6, 12, 8, -6], axis: true});
<script type="text/javascript">
 
    /* <![CDATA[ */
 
 
 
        board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
 
        b1axisx = board.createElement('axis', [[0,0], [1,0]], {});
 
        b1axisy = board.createElement('axis', [[0,0], [0,1]], {});
 
 
 
eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
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eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
graph = board.createElement('functiongraph', [function(x){ return f(x); }, -10, 10]);
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var graph = board.createElement('functiongraph', [function(x){ return f(x); }, -10, 10]),
        p1 = board.createElement('glider', [0,0,graph], {style:6, name:'P'});
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    p1 = board.createElement('glider', [0,0,graph], {style:6, name:'P'}),
        p2 = board.createElement('point', [function() { return p1.X()+1;}, function() {return p1.Y()+board.D(graph.Y)(p1.X());}], {style:1, name:''});
+
    p2 = board.createElement('point', [function() { return p1.X()+1;}, function() {return p1.Y()+board.D(graph.Y)(p1.X());}], {style:1, name:''}),
        l1 = board.createElement('line', [p1,p2],{});
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    l1 = board.createElement('line', [p1,p2],{}),
        p3 = board.createElement('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''});
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    p3 = board.createElement('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''}),
        pol = board.createElement('polygon', [p1,p2,p3], {});
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    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));}]);  
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    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(){
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    function doIt(){
        eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
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        eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
        graph.Y = function(x){ return f(x); };
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        graph.Y = function(x){ return f(x); };
    graph.updateCurve();
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        graph.updateCurve();
    board.update();
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        board.update();
        }  
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    }  
       
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</jsxgraph>
  /* ]]> */
 
  </script>
 
</html>
 
  
  

Revision as of 14:29, 7 June 2011

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', {originX: 250, originY: 250, unitX: 40, unitY: 20});
// Axes
b1axisx = board.createElement('axis', [[0,0], [1,0]], {});
b1axisy = board.createElement('axis', [[0,0], [0,1]], {});

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.createElement('functiongraph', [function(x){ return f(x); },-10, 10]);

Define Further Elements

//glider on the curve
p1 = board.createElement('glider', [0,0,graph], {style:6, name:'P'});
//define the derivative of f
g = board.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.createElement('point', [function() { return p1.X()+1;}, function() {return p1.Y()+board.D(graph.Y)(p1.X());}], {style:1, name:''});
//the tangent 
l1 = board.createElement('line', [p1,p2],{}); 
//a third point fpr the slope triangle
p3 = board.createElement('point', [function() { return p2.X();}, function() {return p1.Y();}],{style:1, name:''});
//the slope triangle
pol = board.createElement('polygon', [p1,p2,p3], {});
//a text for displaying slope's value
//                               variable x coordinate          variable y coordinate                        variable value
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));}],{color:ff0000});

Define JavaScript Function doIt() for Reacting on User Input

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.