tests/linear-regression-fractions.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 = "X,Y1,Y2\n";
  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         data += i + "," + i + "/120," + (i*(120-i)) + "/" + (60*60) + "\n";
  32       }
  33
  34       g = new Dygraph(
  35               document.getElementById("demodiv"),
  36               data,
  37               {
  38                 underlayCallback: drawLines,
  39                 drawPoints: true,
  40                 strokeWidth: 0.0,
  41                 fractions: true,
  42                 errorBars: true,
  43                 pointSize: 1
  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           // Scale up to percentages, rather than fractions.
 109           y1 *= 100;
 110           y2 *= 100;
 111
 112           var p1 = g.toDomCoords(x1, y1);
 113           var p2 = g.toDomCoords(x2, y2);
 114
 115           var c = Dygraph.toRGB_(g.getColors()[i - 1]);
 116           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 117           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 118           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 119           var color = toHex(c);
 120           ctx.save();
 121           ctx.strokeStyle = color;
 122           ctx.lineWidth = 2.0;
 123           ctx.beginPath();
 124           ctx.moveTo(p1[0], p1[1]);
 125           ctx.lineTo(p2[0], p2[1]);
 126           ctx.closePath();
 127           ctx.stroke();
 128           ctx.restore();
 129         }
 130       }
 131
 132     </script>
 133
 134     <div style="position: absolute; left: 500px; top: 150px;">
 135     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 136     <br/><br/>
 137     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 138     <br/><br/>
 139     <input type=button value="Clear Lines" onClick="clearLines()" />
 140     </div>
 141 </body>
 142 </html>