4 <title>Linear Regression
</title>
6 <script type=
"text/javascript" src=
"../excanvas.js"></script>
8 <script type=
"text/javascript" src=
"../strftime/strftime-min.js"></script>
9 <script type=
"text/javascript" src=
"../rgbcolor/rgbcolor.js"></script>
10 <script type=
"text/javascript" src=
"../dygraph-canvas.js"></script>
11 <script type=
"text/javascript" src=
"../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">
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)]);
34 document.getElementById(
"demodiv"),
37 labels: ['X', 'Y1', 'Y2'],
38 underlayCallback: drawLines,
44 // coefficients of regression for each series.
45 // if coeffs = [ null, [
1,
2], null ] then we draw a regression for series
1
46 // only. The regression line is y =
1 +
2 * x.
47 var coeffs = [ null, null, null ];
48 function regression(series) {
49 // Only run the regression over visible points.
50 var range = g.xAxisRange();
52 var sum_xy =
0.0, sum_x =
0.0, sum_y =
0.0, sum_x2 =
0.0, num =
0;
53 for (var i =
0; i < g.numRows(); i++) {
54 var x = g.getValue(i,
0);
55 if (x < range[
0] || x
> range[
1]) continue;
57 var y = g.getValue(i, series);
58 if (y == null) continue;
71 var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
72 var b = (sum_y - a * sum_x) / num;
74 coeffs[series] = [b, a];
75 if (typeof(console) != 'undefined') {
76 console.log(
"coeffs(" + series +
"): [" + b +
", " + a +
"]");
79 g.updateOptions({}); // forces a redraw.
82 function clearLines() {
83 for (var i =
0; i < coeffs.length; i++) coeffs[i] = null;
87 function drawLines(ctx, area, layout) {
88 if (typeof(g) == 'undefined') return; // won't be set on the initial draw.
90 var range = g.xAxisRange();
91 for (var i =
0; i < coeffs.length; i++) {
92 if (!coeffs[i]) continue;
101 var p1 = g.toDomCoords(x1, y1);
102 var p2 = g.toDomCoords(x2, y2);
104 var c = new RGBColor(g.getColors()[i -
1]);
105 c.r = Math.floor(
255 -
0.5 * (
255 - c.r));
106 c.g = Math.floor(
255 -
0.5 * (
255 - c.g));
107 c.b = Math.floor(
255 -
0.5 * (
255 - c.b));
108 var color = c.toHex();
110 ctx.strokeStyle = color;
113 ctx.moveTo(p1[
0], p1[
1]);
114 ctx.lineTo(p2[
0], p2[
1]);
123 <div style=
"position: absolute; left: 500px; top: 150px;">
124 <input type=button
style=
"color: green;" value=
"Regression (Y1)" onClick=
"regression(1)" />
126 <input type=button
style=
"color: blue;" value=
"Regression (Y2)" onClick=
"regression(2)" />
128 <input type=button
value=
"Clear Lines" onClick=
"clearLines()" />