tests/linear-regression-fractions.html

   1 <html>
   2   <head>
   3     <title>Linear Regression</title>
   4     <!--[if IE]>
   5     <script type="text/javascript" src="../excanvas.js"></script>
   6     <![endif]-->
   7     <script type="text/javascript" src="../strftime/strftime-min.js"></script>
   8     <script type="text/javascript" src="../rgbcolor/rgbcolor.js"></script>
   9     <script type="text/javascript" src="../dygraph-canvas.js"></script>
  10     <script type="text/javascript" src="../dygraph.js"></script>
  11     <style type="text/css">
  12     body { max-width: 640 px; }
  13     </style>
  14   </head>
  15   <body>
  16     <h2>Linear Regression Demo</h2>
  17     <p>Click the buttons to generate linear regressions over either data
  18     series. If you zoom in and click the regression button, the regression will
  19     only be run over visible points. Zoom back out to see what the local
  20     regression looks like over the full data.</p>
  21
  22     <div id="demodiv" style="width: 480px; height: 320px;"></div>
  23
  24     <script type="text/javascript">
  25       var data = "X,Y1,Y2\n";
  26       for (var i = 0; i < 120; i++) {
  27         // data.push([i,
  28         //            i / 5.0 + 10.0 * Math.sin(i / 3.0),
  29         //            30.0 - i / 5.0 - 10.0 * Math.sin(i / 3.0 + 1.0)]);
  30         data += i + "," + i + "/120," + (i*(120-i)) + "/" + (60*60) + "\n";
  31       }
  32
  33       g = new Dygraph(
  34               document.getElementById("demodiv"),
  35               data,
  36               {
  37                 underlayCallback: drawLines,
  38                 drawPoints: true,
  39                 strokeWidth: 0.0,
  40                 fractions: true,
  41                 errorBars: true
  42               }
  43           );
  44
  45       // coefficients of regression for each series.
  46       // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
  47       // only. The regression line is y = 1 + 2 * x.
  48       var coeffs = [ null, null, null ];
  49       function regression(series) {
  50         // Only run the regression over visible points.
  51         var range = g.xAxisRange();
  52
  53         var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
  54         for (var i = 0; i < g.numRows(); i++) {
  55           var x = g.getValue(i, 0);
  56           if (x < range[0] || x > range[1]) continue;
  57
  58           var y = g.getValue(i, series);
  59           if (y == null) continue;
  60           if (y.length == 2) {
  61             // using fractions
  62             y = y[0] / y[1];
  63           }
  64
  65           num++;
  66           sum_x += x;
  67           sum_y += y;
  68           sum_xy += x * y;
  69           sum_x2 += x * x;
  70         }
  71
  72         var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
  73         var b = (sum_y - a * sum_x) / num;
  74
  75         coeffs[series] = [b, a];
  76         if (typeof(console) != 'undefined') {
  77           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  78         }
  79
  80         g.updateOptions({});  // forces a redraw.
  81       }
  82
  83       function clearLines() {
  84         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  85         g.updateOptions({});
  86       }
  87
  88       function drawLines(ctx, area, layout) {
  89         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  90
  91         var range = g.xAxisRange();
  92         for (var i = 0; i < coeffs.length; i++) {
  93           if (!coeffs[i]) continue;
  94           var a = coeffs[i][1];
  95           var b = coeffs[i][0];
  96
  97           var x1 = range[0];
  98           var y1 = a * x1 + b;
  99           var x2 = range[1];
 100           var y2 = a * x2 + b;
 101
 102           // Scale up to percentages, rather than fractions.
 103           y1 *= 100;
 104           y2 *= 100;
 105
 106           var p1 = g.toDomCoords(x1, y1);
 107           var p2 = g.toDomCoords(x2, y2);
 108
 109           var c = new RGBColor(g.getColors()[i - 1]);
 110           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 111           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 112           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 113           var color = c.toHex();
 114           ctx.save();
 115           ctx.strokeStyle = color;
 116           ctx.lineWidth = 1.0;
 117           ctx.beginPath();
 118           ctx.moveTo(p1[0], p1[1]);
 119           ctx.lineTo(p2[0], p2[1]);
 120           ctx.closePath();
 121           ctx.stroke();
 122           ctx.restore();
 123         }
 124       }
 125
 126     </script>
 127
 128     <div style="position: absolute; left: 500px; top: 150px;">
 129     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 130     <br/><br/>
 131     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 132     <br/><br/>
 133     <input type=button value="Clear Lines" onClick="clearLines()" />
 134     </div>
 135 </body>
 136 </html>