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 drawLines(ctx, area, layout) {
  91         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  92
  93         var range = g.xAxisRange();
  94         for (var i = 0; i < coeffs.length; i++) {
  95           if (!coeffs[i]) continue;
  96           var a = coeffs[i][1];
  97           var b = coeffs[i][0];
  98
  99           var x1 = range[0];
 100           var y1 = a * x1 + b;
 101           var x2 = range[1];
 102           var y2 = a * x2 + b;
 103
 104           var p1 = g.toDomCoords(x1, y1);
 105           var p2 = g.toDomCoords(x2, y2);
 106
 107           var c = new RGBColor(g.getColors()[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           var color = c.toHex();
 112           ctx.save();
 113           ctx.strokeStyle = color;
 114           ctx.lineWidth = 1.0;
 115           ctx.beginPath();
 116           ctx.moveTo(p1[0], p1[1]);
 117           ctx.lineTo(p2[0], p2[1]);
 118           ctx.closePath();
 119           ctx.stroke();
 120           ctx.restore();
 121         }
 122       }
 123
 124     </script>
 125
 126     <div style="position: absolute; left: 500px; top: 150px;">
 127     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 128     <br/><br/>
 129     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 130     <br/><br/>
 131     <input type=button value="Clear Lines" onClick="clearLines()" />
 132     </div>
 133 </body>
 134 </html>