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)]);
35 var labels = ['X', 'Y1', 'Y2'];
39 document.getElementById(
"demodiv"),
45 drawCallback: function(g, is_initial) {
46 if (!is_initial) return;
47 var c = g.getColors();
48 for (var i =
0; i < c.length; i++) orig_colors.push(c[i]);
53 // coefficients of regression for each series.
54 // if coeffs = [ null, [
1,
2], null ] then we draw a regression for series
1
55 // only. The regression line is y =
1 +
2 * x.
56 var coeffs = [ null, null, null ];
57 function regression(series) {
58 // Only run the regression over visible points.
59 var range = g.xAxisRange();
61 var sum_xy =
0.0, sum_x =
0.0, sum_y =
0.0, sum_x2 =
0.0, num =
0;
62 for (var i =
0; i < data.length; i++) {
64 if (x < range[
0] || x
> range[
1]) continue;
66 var y = data[i][series];
67 if (y == null) continue;
80 var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
81 var b = (sum_y - a * sum_x) / num;
83 coeffs[series] = [b, a];
84 if (typeof(console) != 'undefined') {
85 console.log(
"coeffs(" + series +
"): [" + b +
", " + a +
"]");
92 return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
95 function updateChart() {
96 // Generate a new data set with the regression lines.
100 for (var i =
0; i < labels.length; i++) {
101 new_labels.push(labels[i]);
102 if (i) new_colors.push(orig_colors[i -
1]);
104 // Darken the series by
50% to generate its regression.
105 var label = labels[i] +
" Regression";
106 new_labels.push(label);
107 var c = Dygraph.toRGB_(orig_colors[i -
1]);
108 c.r = Math.floor(
255 -
0.5 * (
255 - c.r));
109 c.g = Math.floor(
255 -
0.5 * (
255 - c.g));
110 c.b = Math.floor(
255 -
0.5 * (
255 - c.b));
111 new_colors.push(toHex(c));
120 for (var i =
0; i < data.length; i++) {
122 for (var j =
0; j < data[i].length; j++) {
123 new_data[i].push(data[i][j]);
125 new_data[i].push(coeffs[j][
0] + coeffs[j][
1] * data[i][
0]);
130 new_opts.file = new_data;
131 new_opts.labels = new_labels;
132 new_opts.colors = new_colors;
133 g.updateOptions(new_opts);
136 function clearLines() {
137 for (var i =
0; i < coeffs.length; i++) coeffs[i] = null;
143 <div style=
"position: absolute; left: 500px; top: 150px;">
144 <input type=button
style=
"color: green;" value=
"Regression (Y1)" onClick=
"regression(1)" />
146 <input type=button
style=
"color: blue;" value=
"Regression (Y2)" onClick=
"regression(2)" />
148 <input type=button
value=
"Clear Lines" onClick=
"clearLines()" />