Change Equation of a Graph

2008-09-15T14:31:54Z

WikiSysop:

This example shows how you can change the equation of a graph without creating the whole construction again.
<html>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/prototype.js"></script>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/loadjsxgraphXML.js"></script>
<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; float:left; "></div>
<p style="float:right">
<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">

<input type="button" value="set" onClick="doIt()" style='margin:1em'>
</p>
</div>
<br clear=all>
<div id="debug" style="display:none;"></div>
<script type="text/javascript">
/* <![CDATA[ */

board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
// Axes
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'});
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.Y = function(x){ return f(x); };
graph.updateCurve();
board.update();
}

/* ]]> */
</script>
</html>

== How to Create this Construction ==

=== HTML Part ===
'''Adding a text input field somewhere on the page together with a button'''

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

=== JavaScript Part ===
'''Setting up the board'''
<source lang="javascript">
board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
// Axes
b1axisx = board.createElement('axis', [[1,0], [0,0]], {});
b1axisy = board.createElement('axis', [[0,1], [0,0]], {});
</source>

'''Create a JavaScript Function f(x) From the Text Field'''
<source lang="javascript">
eval("function f(x){ return "+document.getElementById("eingabe").value+";}");
</source>

'''Use f(x) for defining the Graph'''
<source lang="javascript">
graph = board.createElement('curve', [function(x){ return x; }, function(x){ return f(x); }, "x", -10, 10]);
</source>

'''Define Further Elements'''
<source lang="javascript">
//glider on the curve
p1 = board.createElement('glider', [graph], {style:6, name:'P'});
//define the derivative of f
g = board.algebra.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.algebra.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});
</source>

'''Define JavaScript Function doIt() for Reacting on User Input'''
<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 aononymous functions of JavaScript.
[[Category:Examples]]

MediaWiki:Sidebar

2008-09-15T14:27:37Z

WikiSysop:

MediaWiki:Sidebar

2008-09-15T14:27:20Z

WikiSysop:

MediaWiki:Sidebar

2008-09-15T14:25:34Z

WikiSysop:

MediaWiki:Sidebar

2008-09-15T14:24:50Z

WikiSysop:

MediaWiki:Sidebar

2008-09-15T14:23:30Z

Change Equation of a Graph

2008-09-15T14:17:36Z

WikiSysop:

2008-09-15T09:59:20Z

WikiSysop:

This example shows how you can change the equation of a graph without creating the whole construction again.
<html>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/prototype.js"></script>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/loadjsxgraphXML.js"></script>
<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; float:left; "></div>
<p style="float:right">
<input type="text" id="eingabe" value="Math.sin(x)*Math.cos(x)">

<input type="button" value="set" onClick="doIt()" style='margin:1em'>
</p>
</div>
<br clear=all>
<div id="debug" style="display:none;"></div>
<script type="text/javascript">
/* <![CDATA[ */

board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
// Axes
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>
</html>

== HowTo Create this Construction ==

=== HTML Part ===
'''Adding a text input field somewhere on the page together with a button'''

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

=== JavaScript Part ===
'''Setting up the board'''
<source>
board = JXG.JSXGraph.initBoard('jxgbox', {originX: 250, originY: 250, unitX: 40, unitY: 20});
// Axes
b1axisx = board.createElement('axis', [[1,0], [0,0]], {});
b1axisy = board.createElement('axis', [[0,1], [0,0]], {});
</source>

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

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

'''Use f(x) for defining the Graph'''

<source>
graph = board.createElement('curve', [function(x){ return x; }, function(x){ return f(x); }, "x", -10, 10]);
</source>

'''Define Further Elements'''

<source>
//glider on the curve
p1 = board.createElement('glider', [graph], {style:6, name:'P'});

//define the derivative of f
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:''}); // apoint on the tangent
l1 = board.createElement('line', [p1,p2],{}); // the tangent
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));}]);
</source>

Change Equation of a Graph

2008-09-15T09:48:55Z

WikiSysop:

Change Equation of a Graph

2008-09-15T09:45:54Z

WikiSysop:

Change Equation of a Graph

2008-09-15T09:43:39Z

WikiSysop: