4 <meta http-equiv=
"X-UA-Compatible" content=
"IE=EmulateIE7; IE=EmulateIE9">
5 <title>Linear Regression
</title>
7 <script type=
"text/javascript" src=
"../excanvas.js"></script>
10 For production (minified) code, use:
11 <script type=
"text/javascript" src=
"dygraph-combined.js"></script>
13 <script type=
"text/javascript" src=
"../dygraph-dev.js"></script>
15 <style type=
"text/css">
16 body { max-width:
640 px; }
20 <h2>Linear Regression Demo
</h2>
21 <p>Click the buttons to generate linear regressions over either data
22 series. If you zoom in and click the regression button, the regression will
23 only be run over visible points. Zoom back out to see what the local
24 regression looks like over the full data.
</p>
26 <div id=
"demodiv" style=
"width: 480px; height: 320px;"></div>
28 <script type=
"text/javascript">
30 for (var i =
0; i <
120; i++) {
32 i /
5.0 +
10.0 * Math.sin(i /
3.0),
33 30.0 - i /
5.0 -
10.0 * Math.sin(i /
3.0 +
1.0)]);
37 document.getElementById(
"demodiv"),
40 labels: ['X', 'Y1', 'Y2'],
41 underlayCallback: drawLines,
47 // coefficients of regression for each series.
48 // if coeffs = [ null, [
1,
2], null ] then we draw a regression for series
1
49 // only. The regression line is y =
1 +
2 * x.
50 var coeffs = [ null, null, null ];
51 function regression(series) {
52 // Only run the regression over visible points.
53 var range = g.xAxisRange();
55 var sum_xy =
0.0, sum_x =
0.0, sum_y =
0.0, sum_x2 =
0.0, num =
0;
56 for (var i =
0; i < g.numRows(); i++) {
57 var x = g.getValue(i,
0);
58 if (x < range[
0] || x
> range[
1]) continue;
60 var y = g.getValue(i, series);
61 if (y == null) continue;
74 var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
75 var b = (sum_y - a * sum_x) / num;
77 coeffs[series] = [b, a];
78 if (typeof(console) != 'undefined') {
79 console.log(
"coeffs(" + series +
"): [" + b +
", " + a +
"]");
82 g.updateOptions({}); // forces a redraw.
85 function clearLines() {
86 for (var i =
0; i < coeffs.length; i++) coeffs[i] = null;
91 return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
94 function drawLines(ctx, area, layout) {
95 if (typeof(g) == 'undefined') return; // won't be set on the initial draw.
97 var range = g.xAxisRange();
98 for (var i =
0; i < coeffs.length; i++) {
99 if (!coeffs[i]) continue;
100 var a = coeffs[i][
1];
101 var b = coeffs[i][
0];
108 var p1 = g.toDomCoords(x1, y1);
109 var p2 = g.toDomCoords(x2, y2);
111 var c = Dygraph.toRGB_(g.getColors()[i -
1]);
112 c.r = Math.floor(
255 -
0.5 * (
255 - c.r));
113 c.g = Math.floor(
255 -
0.5 * (
255 - c.g));
114 c.b = Math.floor(
255 -
0.5 * (
255 - c.b));
115 var color = toHex(c);
117 ctx.strokeStyle = color;
120 ctx.moveTo(p1[
0], p1[
1]);
121 ctx.lineTo(p2[
0], p2[
1]);
130 <div style=
"position: absolute; left: 500px; top: 150px;">
131 <input type=button
style=
"color: green;" value=
"Regression (Y1)" onClick=
"regression(1)" />
133 <input type=button
style=
"color: blue;" value=
"Regression (Y2)" onClick=
"regression(2)" />
135 <input type=button
value=
"Clear Lines" onClick=
"clearLines()" />