tests/linear-regression.html

   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
  36       g = new Dygraph(
  37               document.getElementById("demodiv"),
  38               data,
  39               {
  40                 labels: ['X', 'Y1', 'Y2'],
  41                 underlayCallback: drawLines,
  42                 drawPoints: true,
  43                 strokeWidth: 0.0
  44               }
  45           );
  46
  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();
  54
  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;
  59
  60           var y = g.getValue(i, series);
  61           if (y == null) continue;
  62           if (y.length == 2) {
  63             // using fractions
  64             y = y[0] / y[1];
  65           }
  66
  67           num++;
  68           sum_x += x;
  69           sum_y += y;
  70           sum_xy += x * y;
  71           sum_x2 += x * x;
  72         }
  73
  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;
  76
  77         coeffs[series] = [b, a];
  78         if (typeof(console) != 'undefined') {
  79           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  80         }
  81
  82         g.updateOptions({});  // forces a redraw.
  83       }
  84
  85       function clearLines() {
  86         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  87         g.updateOptions({});
  88       }
  89
  90       function toHex(rgb) {
  91         return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
  92       }
  93
  94       function drawLines(ctx, area, layout) {
  95         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  96
  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];
 102
 103           var x1 = range[0];
 104           var y1 = a * x1 + b;
 105           var x2 = range[1];
 106           var y2 = a * x2 + b;
 107
 108           var p1 = g.toDomCoords(x1, y1);
 109           var p2 = g.toDomCoords(x2, y2);
 110
 111           var c = Dygraph.toRGB_(g.getColors()[i - 1]);
 112           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 113           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 114           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 115           var color = toHex(c);
 116           ctx.save();
 117           ctx.strokeStyle = color;
 118           ctx.lineWidth = 1.0;
 119           ctx.beginPath();
 120           ctx.moveTo(p1[0], p1[1]);
 121           ctx.lineTo(p2[0], p2[1]);
 122           ctx.closePath();
 123           ctx.stroke();
 124           ctx.restore();
 125         }
 126       }
 127
 128     </script>
 129
 130     <div style="position: absolute; left: 500px; top: 150px;">
 131     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 132     <br/><br/>
 133     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 134     <br/><br/>
 135     <input type=button value="Clear Lines" onClick="clearLines()" />
 136     </div>
 137 </body>
 138 </html>