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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Linear Regression</title>
<link rel="stylesheet" type="text/css" href="../dist/dygraph.css" />
<link rel="stylesheet" type="text/css" href="../common/vextlnk.css" />
<script type="text/javascript" src="../dist/dygraph.js"></script>
<style type="text/css">
body { max-width: 640 px; }
</style>
</head>
<body>
<h2>Linear Regression Demo</h2>
<p>Click the buttons to generate linear regressions over either data
series. If you zoom in and click the regression button, the regression will
only be run over visible points. Zoom back out to see what the local
regression looks like over the full data.</p>
<div id="demodiv" style="width: 480px; height: 320px;"></div>
<script type="text/javascript"><!--//--><![CDATA[//><!--
Dygraph.onDOMready(function onDOMready() {
var data = [];
for (var i = 0; i < 120; i++) {
data.push([i,
i / 5.0 + 10.0 * Math.sin(i / 3.0),
30.0 - i / 5.0 - 10.0 * Math.sin(i / 3.0 + 1.0)]);
}
g = new Dygraph(
document.getElementById("demodiv"),
data,
{
labels: ['X', 'Y1', 'Y2'],
underlayCallback: drawLines,
drawPoints: true,
strokeWidth: 0.0
}
);
// coefficients of regression for each series.
// if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
// only. The regression line is y = 1 + 2 * x.
var coeffs = [ null, null, null ];
regression = function regression(series) {
// Only run the regression over visible points.
var range = g.xAxisRange();
var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
for (var i = 0; i < g.numRows(); i++) {
var x = g.getValue(i, 0);
if (x < range[0] || x > range[1]) continue;
var y = g.getValue(i, series);
if (y == null) continue;
if (y.length == 2) {
// using fractions
y = y[0] / y[1];
}
num++;
sum_x += x;
sum_y += y;
sum_xy += x * y;
sum_x2 += x * x;
}
var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
var b = (sum_y - a * sum_x) / num;
coeffs[series] = [b, a];
if (typeof(console) != 'undefined') {
console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
}
g.updateOptions({}); // forces a redraw.
}
clearLines = function clearLines() {
for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
g.updateOptions({});
}
function toHex(rgb) {
return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
}
function drawLines(ctx, area, layout) {
if (typeof(g) == 'undefined') return; // won't be set on the initial draw.
var range = g.xAxisRange();
for (var i = 0; i < coeffs.length; i++) {
if (!coeffs[i]) continue;
var a = coeffs[i][1];
var b = coeffs[i][0];
var x1 = range[0];
var y1 = a * x1 + b;
var x2 = range[1];
var y2 = a * x2 + b;
var p1 = g.toDomCoords(x1, y1);
var p2 = g.toDomCoords(x2, y2);
var c = Dygraph.toRGB_(g.getColors()[i - 1]);
c.r = Math.floor(255 - 0.5 * (255 - c.r));
c.g = Math.floor(255 - 0.5 * (255 - c.g));
c.b = Math.floor(255 - 0.5 * (255 - c.b));
var color = toHex(c);
ctx.save();
ctx.strokeStyle = color;
ctx.lineWidth = 1.0;
ctx.beginPath();
ctx.moveTo(p1[0], p1[1]);
ctx.lineTo(p2[0], p2[1]);
ctx.closePath();
ctx.stroke();
ctx.restore();
}
}
});
//--><!]]></script>
<div style="position: absolute; left: 500px; top: 150px;">
<input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
<br /><br />
<input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
<br /><br />
<input type=button value="Clear Lines" onClick="clearLines()" />
</div>
</body>
</html>
|
