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1<!DOCTYPE html>
2<html>
3 <head>
4 <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9">
5 <title>Linear Regression</title>
6 <!--[if IE]>
7 <script type="text/javascript" src="../excanvas.js"></script>
8 <![endif]-->
9 <!--
10 For production (minified) code, use:
11 <script type="text/javascript" src="dygraph-combined.js"></script>
12 -->
13 <script type="text/javascript" src="../dygraph-dev.js"></script>
14
15 <style type="text/css">
16 body { max-width: 640 px; }
17 </style>
18 </head>
19 <body>
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>
25
26 <div id="demodiv" style="width: 480px; height: 320px;"></div>
27
28 <script type="text/javascript">
29 var data = [];
30 for (var i = 0; i < 120; i++) {
31 data.push([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)]);
34 }
35 var labels = ['X', 'Y1', 'Y2'];
36 var orig_colors = [];
37
38 g = new Dygraph(
39 document.getElementById("demodiv"),
40 data,
41 {
42 labels: labels,
43 drawPoints: true,
44 strokeWidth: 0.0,
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]);
49 }
50 }
51 );
52
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();
60
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++) {
63 var x = data[i][0];
64 if (x < range[0] || x > range[1]) continue;
65
66 var y = data[i][series];
67 if (y == null) continue;
68 if (y.length == 2) {
69 // using fractions
70 y = y[0] / y[1];
71 }
72
73 num++;
74 sum_x += x;
75 sum_y += y;
76 sum_xy += x * y;
77 sum_x2 += x * x;
78 }
79
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;
82
83 coeffs[series] = [b, a];
84 if (typeof(console) != 'undefined') {
85 console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
86 }
87
88 updateChart();
89 }
90
91 function toHex(rgb) {
92 return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
93 }
94
95 function updateChart() {
96 // Generate a new data set with the regression lines.
97 var new_labels = [];
98 var new_colors = [];
99 var new_opts = {};
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]);
103 if (coeffs[i]) {
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));
112 new_opts[label] = {
113 drawPoints: false,
114 strokeWidth: 1.0
115 };
116 }
117 }
118
119 var new_data = [];
120 for (var i = 0; i < data.length; i++) {
121 new_data.push([]);
122 for (var j = 0; j < data[i].length; j++) {
123 new_data[i].push(data[i][j]);
124 if (coeffs[j]) {
125 new_data[i].push(coeffs[j][0] + coeffs[j][1] * data[i][0]);
126 }
127 }
128 }
129
130 new_opts.file = new_data;
131 new_opts.labels = new_labels;
132 new_opts.colors = new_colors;
133 g.updateOptions(new_opts);
134 }
135
136 function clearLines() {
137 for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
138 updateChart();
139 }
140
141 </script>
142
143 <div style="position: absolute; left: 500px; top: 150px;">
144 <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
145 <br/><br/>
146 <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
147 <br/><br/>
148 <input type=button value="Clear Lines" onClick="clearLines()" />
149 </div>
150</body>
151</html>