tests/linear-regression.html

   1 <!DOCTYPE html>
   2 <html>
   3   <head>
   4     <link rel="stylesheet" href="../css/dygraph.css">
   5     <title>Linear Regression</title>
   6     <!--
   7     For production (minified) code, use:
   8     <script type="text/javascript" src="dygraph-combined.js"></script>
   9     -->
  10     <script type="text/javascript" src="../dist/dygraph.js"></script>
  11
  12     <style type="text/css">
  13     body { max-width: 640 px; }
  14     </style>
  15   </head>
  16   <body>
  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>
  22
  23     <div id="demodiv" style="width: 480px; height: 320px;"></div>
  24
  25     <script type="text/javascript">
  26       var data = [];
  27       for (var i = 0; i < 120; i++) {
  28         data.push([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       }
  32
  33       g = new Dygraph(
  34               document.getElementById("demodiv"),
  35               data,
  36               {
  37                 labels: ['X', 'Y1', 'Y2'],
  38                 underlayCallback: drawLines,
  39                 drawPoints: true,
  40                 strokeWidth: 0.0
  41               }
  42           );
  43
  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();
  51
  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;
  56
  57           var y = g.getValue(i, series);
  58           if (y == null) continue;
  59           if (y.length == 2) {
  60             // using fractions
  61             y = y[0] / y[1];
  62           }
  63
  64           num++;
  65           sum_x += x;
  66           sum_y += y;
  67           sum_xy += x * y;
  68           sum_x2 += x * x;
  69         }
  70
  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;
  73
  74         coeffs[series] = [b, a];
  75         if (typeof(console) != 'undefined') {
  76           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  77         }
  78
  79         g.updateOptions({});  // forces a redraw.
  80       }
  81
  82       function clearLines() {
  83         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  84         g.updateOptions({});
  85       }
  86
  87       function toHex(rgb) {
  88         return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
  89       }
  90
  91       function drawLines(ctx, area, layout) {
  92         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  93
  94         var range = g.xAxisRange();
  95         for (var i = 0; i < coeffs.length; i++) {
  96           if (!coeffs[i]) continue;
  97           var a = coeffs[i][1];
  98           var b = coeffs[i][0];
  99
 100           var x1 = range[0];
 101           var y1 = a * x1 + b;
 102           var x2 = range[1];
 103           var y2 = a * x2 + b;
 104
 105           var p1 = g.toDomCoords(x1, y1);
 106           var p2 = g.toDomCoords(x2, y2);
 107
 108           var c = Dygraph.toRGB_(g.getColors()[i - 1]);
 109           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 110           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 111           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 112           var color = toHex(c);
 113           ctx.save();
 114           ctx.strokeStyle = color;
 115           ctx.lineWidth = 1.0;
 116           ctx.beginPath();
 117           ctx.moveTo(p1[0], p1[1]);
 118           ctx.lineTo(p2[0], p2[1]);
 119           ctx.closePath();
 120           ctx.stroke();
 121           ctx.restore();
 122         }
 123       }
 124
 125     </script>
 126
 127     <div style="position: absolute; left: 500px; top: 150px;">
 128     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 129     <br/><br/>
 130     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 131     <br/><br/>
 132     <input type=button value="Clear Lines" onClick="clearLines()" />
 133     </div>
 134 </body>
 135 </html>