4 <link rel=
"stylesheet" href=
"../css/dygraph.css">
5 <title>Linear Regression
</title>
7 For production (minified) code, use:
8 <script type=
"text/javascript" src=
"dygraph-combined.js"></script>
10 <script type=
"text/javascript" src=
"../dist/dygraph.js"></script>
12 <style type=
"text/css">
13 body { max-width:
640 px; }
17 <h2>Linear Regression Demo
</h2>
18 <p>Click the buttons to generate linear regressions over either data
19 series. If you zoom in and click the regression button, the regression will
20 only be run over visible points. Zoom back out to see what the local
21 regression looks like over the full data.
</p>
23 <div id=
"demodiv" style=
"width: 480px; height: 320px;"></div>
25 <script type=
"text/javascript">
26 var data =
"X,Y1,Y2\n";
27 for (var i =
0; i <
120; i++) {
29 // i /
5.0 +
10.0 * Math.sin(i /
3.0),
30 //
30.0 - i /
5.0 -
10.0 * Math.sin(i /
3.0 +
1.0)]);
31 data += i +
"," + i +
"/120," + (i*(
120-i)) +
"/" + (
60*
60) +
"\n";
35 document.getElementById(
"demodiv"),
38 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 // Scale up to percentages, rather than fractions.
112 var p1 = g.toDomCoords(x1, y1);
113 var p2 = g.toDomCoords(x2, y2);
115 var c = Dygraph.toRGB_(g.getColors()[i -
1]);
116 c.r = Math.floor(
255 -
0.5 * (
255 - c.r));
117 c.g = Math.floor(
255 -
0.5 * (
255 - c.g));
118 c.b = Math.floor(
255 -
0.5 * (
255 - c.b));
119 var color = toHex(c);
121 ctx.strokeStyle = color;
124 ctx.moveTo(p1[
0], p1[
1]);
125 ctx.lineTo(p2[
0], p2[
1]);
134 <div style=
"position: absolute; left: 500px; top: 150px;">
135 <input type=button
style=
"color: green;" value=
"Regression (Y1)" onClick=
"regression(1)" />
137 <input type=button
style=
"color: blue;" value=
"Regression (Y2)" onClick=
"regression(2)" />
139 <input type=button
value=
"Clear Lines" onClick=
"clearLines()" />