tests/linear-regression-fractions.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 = "X,Y1,Y2\n";
  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         data += i + "," + i + "/120," + (i*(120-i)) + "/" + (60*60) + "\n";
  35       }
  36
  37       g = new Dygraph(
  38               document.getElementById("demodiv"),
  39               data,
  40               {
  41                 underlayCallback: drawLines,
  42                 drawPoints: true,
  43                 strokeWidth: 0.0,
  44                 fractions: true,
  45                 errorBars: true
  46               }
  47           );
  48
  49       // coefficients of regression for each series.
  50       // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
  51       // only. The regression line is y = 1 + 2 * x.
  52       var coeffs = [ null, null, null ];
  53       function regression(series) {
  54         // Only run the regression over visible points.
  55         var range = g.xAxisRange();
  56
  57         var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
  58         for (var i = 0; i < g.numRows(); i++) {
  59           var x = g.getValue(i, 0);
  60           if (x < range[0] || x > range[1]) continue;
  61
  62           var y = g.getValue(i, series);
  63           if (y == null) continue;
  64           if (y.length == 2) {
  65             // using fractions
  66             y = y[0] / y[1];
  67           }
  68
  69           num++;
  70           sum_x += x;
  71           sum_y += y;
  72           sum_xy += x * y;
  73           sum_x2 += x * x;
  74         }
  75
  76         var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
  77         var b = (sum_y - a * sum_x) / num;
  78
  79         coeffs[series] = [b, a];
  80         if (typeof(console) != 'undefined') {
  81           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  82         }
  83
  84         g.updateOptions({});  // forces a redraw.
  85       }
  86
  87       function clearLines() {
  88         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  89         g.updateOptions({});
  90       }
  91
  92       function drawLines(ctx, area, layout) {
  93         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  94
  95         var range = g.xAxisRange();
  96         for (var i = 0; i < coeffs.length; i++) {
  97           if (!coeffs[i]) continue;
  98           var a = coeffs[i][1];
  99           var b = coeffs[i][0];
 100
 101           var x1 = range[0];
 102           var y1 = a * x1 + b;
 103           var x2 = range[1];
 104           var y2 = a * x2 + b;
 105
 106           // Scale up to percentages, rather than fractions.
 107           y1 *= 100;
 108           y2 *= 100;
 109
 110           var p1 = g.toDomCoords(x1, y1);
 111           var p2 = g.toDomCoords(x2, y2);
 112
 113           var c = new RGBColor(g.getColors()[i - 1]);
 114           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 115           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 116           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 117           var color = c.toHex();
 118           ctx.save();
 119           ctx.strokeStyle = color;
 120           ctx.lineWidth = 1.0;
 121           ctx.beginPath();
 122           ctx.moveTo(p1[0], p1[1]);
 123           ctx.lineTo(p2[0], p2[1]);
 124           ctx.closePath();
 125           ctx.stroke();
 126           ctx.restore();
 127         }
 128       }
 129
 130     </script>
 131
 132     <div style="position: absolute; left: 500px; top: 150px;">
 133     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 134     <br/><br/>
 135     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 136     <br/><br/>
 137     <input type=button value="Clear Lines" onClick="clearLines()" />
 138     </div>
 139 </body>
 140 </html>