tests/linear-regression-fractions.html

   1 <!DOCTYPE html>
   2 <html>
   3   <head>
   4     <link rel="stylesheet" href="../dist/dygraph.css">
   5     <title>Linear Regression</title>
   6     <script type="text/javascript" src="../dist/dygraph.js"></script>
   7
   8     <style type="text/css">
   9     body { max-width: 640 px; }
  10     </style>
  11   </head>
  12   <body>
  13     <h2>Linear Regression Demo</h2>
  14     <p>Click the buttons to generate linear regressions over either data
  15     series. If you zoom in and click the regression button, the regression will
  16     only be run over visible points. Zoom back out to see what the local
  17     regression looks like over the full data.</p>
  18
  19     <div id="demodiv" style="width: 480px; height: 320px;"></div>
  20
  21     <script type="text/javascript">
  22       var data = "X,Y1,Y2\n";
  23       for (var i = 0; i < 120; i++) {
  24         // data.push([i,
  25         //            i / 5.0 + 10.0 * Math.sin(i / 3.0),
  26         //            30.0 - i / 5.0 - 10.0 * Math.sin(i / 3.0 + 1.0)]);
  27         data += i + "," + i + "/120," + (i*(120-i)) + "/" + (60*60) + "\n";
  28       }
  29
  30       g = new Dygraph(
  31               document.getElementById("demodiv"),
  32               data,
  33               {
  34                 underlayCallback: drawLines,
  35                 drawPoints: true,
  36                 strokeWidth: 0.0,
  37                 fractions: true,
  38                 errorBars: true,
  39                 pointSize: 1
  40               }
  41           );
  42
  43       // coefficients of regression for each series.
  44       // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
  45       // only. The regression line is y = 1 + 2 * x.
  46       var coeffs = [ null, null, null ];
  47       function regression(series) {
  48         // Only run the regression over visible points.
  49         var range = g.xAxisRange();
  50
  51         var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
  52         for (var i = 0; i < g.numRows(); i++) {
  53           var x = g.getValue(i, 0);
  54           if (x < range[0] || x > range[1]) continue;
  55
  56           var y = g.getValue(i, series);
  57           if (y == null) continue;
  58           if (y.length == 2) {
  59             // using fractions
  60             y = y[0] / y[1];
  61           }
  62
  63           num++;
  64           sum_x += x;
  65           sum_y += y;
  66           sum_xy += x * y;
  67           sum_x2 += x * x;
  68         }
  69
  70         var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
  71         var b = (sum_y - a * sum_x) / num;
  72
  73         coeffs[series] = [b, a];
  74         if (typeof(console) != 'undefined') {
  75           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  76         }
  77
  78         g.updateOptions({});  // forces a redraw.
  79       }
  80
  81       function clearLines() {
  82         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  83         g.updateOptions({});
  84       }
  85
  86       function toHex(rgb) {
  87         return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
  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           // Scale up to percentages, rather than fractions.
 105           y1 *= 100;
 106           y2 *= 100;
 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 = 2.0;
 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>