Function Grapher

Stephane Gamondes Sep 9, 2000

Graphs any function you enter on the scale of your choice, assuming you use the correct JavaScript syntax. For example, to use Cos x, use Math.cos(x). Or, for x^2, use Math.pow(x, 2), etc.

The JavaScript Source: Math Related: Function Grapher (Function Page)

Simply click inside the window below, use your cursor to highlight the script, and copy (type Control-c or Apple-c) the script into a new file in your text editor (such as Note Pad or Simple Text) and save (Control-s or Apple-s). The script is yours!!!

<!-- THREE STEPS TO INSTALL FUNCTION GRAPHER:

1.  Copy the coding into the HEAD of your HTML document
  2.  Add the last code into the BODY of your HTML document
  3.  Paste the final coding into a new file, drawGraph.html  -->

<HEAD>

</script>
</HEAD>

<BODY>

<center>
<form>
<table border=0 bgcolor="#E6E6E6" cellpadding=3 cellspacing=0>
<tr>
<td colspan=2>
<font face="Arial" size="2">Function (JavaScript syntax)<br>
<input type=text name=graph size=20 maxlength=40 value="Math.cos(x)">
<p>
<td rowspan=2 valign=middle align=center> 
<input type=button value="Plot" name=Plot onClick="drawGraph(this.form)">   
</td>
</tr>
<tr>
<td nowrap>
<font face="Arial" size="2">X min<br>
<input type=text name=minX size=4 maxlength=3 value="-10">
</font>
</td>
<td nowrap>
<font face="Arial" size="2">X max<br>
<input type=text name=maxX size=3 maxlength=3 value="10">
</font>
</td>
</tr>
</table>
</form>
</center>

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The JavaScript Source: Math Related: Function Grapher (Draw Graph Page)

<!-- TWO STEPS TO INSTALL FUNCTION GRAPHER:

1.  Paste this HTML code into a new file, name it drawGraph.html
  2.  Save the necessary images to your web site directory  -->

<html>
<head>
</head>
<style>
.point
{
position: absolute;
}
</style>

dotCode = '<div class="point" id="pdot_id"><img src="graph.gif" width="1" height="pic_height" alt="pic_alt"></div>\n';
xCode = '<div class="point" id="xAxis"><table border="0" width="x_width" cellspacing="0" cellpadding="0"><tr><td width="100%" bgcolor="#000000"><img src="espace.gif" width="1" height="1"></td></tr></table></div>\n';
yCode = '<div class="point" id="yAxis"><table border="0" height="y_height" cellspacing="0" cellpadding="0"><tr><td width="100%" bgcolor="#000000"><img src="espace.gif" width="1" height="1"></td></tr></table></div>\n';
backCode = '<div class="point" id="background"><table border="0" height="back_height" width="back_width" cellspacing="0" cellpadding="0"><tr><td width="100%" bgcolor="#EEEEEE"> </td></tr></table></div>\n';

if (navigator.appName == 'Netscape')
{
leftCode = 'document.obj_id.left = ';
topCode = 'document.obj_id.top = ';
}
else
{
leftCode = 'document.all.obj_id.style.left = ';
topCode = 'document.all.obj_id.style.top = ';
}

params = getParams();
fct = unescape(params["graph"]);
xMin = parseFloat(params["minX"]); xMax = parseFloat(params["maxX"]);
nbXs =200; nbYs = 200;
maxYpos = 225; minXpos = 25;
x = xMin;
yZero = Math.abs(eval(fct));
yMax = yZero;
yMin = yZero;
datas = new Array();

deltaX = (xMax - xMin) / nbXs;

i = 0;
while (x <= xMax)
{
y = eval(fct);
datas[i] = x + ':' + y;
yMax = Math.max(y, yMax);
yMin = Math.min(y, yMin);
yZero = Math.min(yZero, Math.abs(y))
x+= deltaX; i++;
}

deltaY = nbYs / (yMax - yMin);

yPos = new Array();
for (i=0; i<datas.length; i++)
{
yPos[i] = maxYpos - (((datas[i].split(':'))[1] - yMin) * deltaY);
}

document.write(backCode.replace(/back_width/, nbXs).replace(/back_height/, nbYs));
eval(leftCode.replace(/obj_id/, 'background') + minXpos);
eval(topCode.replace(/obj_id/, 'background') + (maxYpos - nbYs));

if ((xMin * xMax) < 0)
{
document.write(yCode.replace(/y_height/, nbXs));
eval(leftCode.replace(/obj_id/, 'yAxis') + (minXpos - (xMin * (nbXs/(xMax - xMin)))));
eval(topCode.replace(/obj_id/, 'yAxis') + (maxYpos - nbYs));
}

if ((yMin * yMax) <= 0)
{
document.write(xCode.replace(/x_width/, nbYs));
eval(leftCode.replace(/obj_id/, 'xAxis') + minXpos);
eval(topCode.replace(/obj_id/, 'xAxis') + (maxYpos - ((yZero - yMin) * deltaY)));
}

for (i=1; i<(datas.length-1); i++)
{
picHeight = Math.abs((yPos[i-1] - yPos[i]) + (yPos[i] - yPos[i+1])) / 2;
YDPos = yPos[i] - (Math.round(picHeight) / 2);
document.write(dotCode.replace(/dot_id/, i).replace(/pic_height/, Math.ceil(picHeight)).replace(/pic_alt/, datas[i]));
eval(leftCode.replace(/obj_id/, 'p' + i) + (minXpos + i));
eval(topCode.replace(/obj_id/, 'p' + i) + YDPos);
}

</script>
<body bgcolor="#FFFFFF">
</body>
</html>

<!-- STEP FOUR: Point your web browser to:

http://www.javascriptsource.com/img/function-grapher/function-grapher.zip

This file contains the two necessary images for your function grapher JavaScript to work.

Upload these files to your web site directory.  -->

Did you use this script? Do you like this site? Please link to us!

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