tests/linear-regression-fractions.html

   1 <!DOCTYPE html>
   2 <html>
   3   <head>
   4     <title>Linear Regression</title>
   5     <!--
   6     For production (minified) code, use:
   7     <script type="text/javascript" src="dygraph-combined.js"></script>
   8     -->
   9     <script type="text/javascript" src="../dygraph-dev.js"></script>
  10
  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                 pointSize: 1
  43               }
  44           );
  45
  46       // coefficients of regression for each series.
  47       // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
  48       // only. The regression line is y = 1 + 2 * x.
  49       var coeffs = [ null, null, null ];
  50       function regression(series) {
  51         // Only run the regression over visible points.
  52         var range = g.xAxisRange();
  53
  54         var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
  55         for (var i = 0; i < g.numRows(); i++) {
  56           var x = g.getValue(i, 0);
  57           if (x < range[0] || x > range[1]) continue;
  58
  59           var y = g.getValue(i, series);
  60           if (y == null) continue;
  61           if (y.length == 2) {
  62             // using fractions
  63             y = y[0] / y[1];
  64           }
  65
  66           num++;
  67           sum_x += x;
  68           sum_y += y;
  69           sum_xy += x * y;
  70           sum_x2 += x * x;
  71         }
  72
  73         var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
  74         var b = (sum_y - a * sum_x) / num;
  75
  76         coeffs[series] = [b, a];
  77         if (typeof(console) != 'undefined') {
  78           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  79         }
  80
  81         g.updateOptions({});  // forces a redraw.
  82       }
  83
  84       function clearLines() {
  85         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  86         g.updateOptions({});
  87       }
  88
  89       function toHex(rgb) {
  90         return 'rgb(' + rgb.r + ',' + rgb.g + ',' + rgb.b + ')';
  91       }
  92
  93       function drawLines(ctx, area, layout) {
  94         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  95
  96         var range = g.xAxisRange();
  97         for (var i = 0; i < coeffs.length; i++) {
  98           if (!coeffs[i]) continue;
  99           var a = coeffs[i][1];
 100           var b = coeffs[i][0];
 101
 102           var x1 = range[0];
 103           var y1 = a * x1 + b;
 104           var x2 = range[1];
 105           var y2 = a * x2 + b;
 106
 107           // Scale up to percentages, rather than fractions.
 108           y1 *= 100;
 109           y2 *= 100;
 110
 111           var p1 = g.toDomCoords(x1, y1);
 112           var p2 = g.toDomCoords(x2, y2);
 113
 114           var c = Dygraph.toRGB_(g.getColors()[i - 1]);
 115           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 116           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 117           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 118           var color = toHex(c);
 119           ctx.save();
 120           ctx.strokeStyle = color;
 121           ctx.lineWidth = 2.0;
 122           ctx.beginPath();
 123           ctx.moveTo(p1[0], p1[1]);
 124           ctx.lineTo(p2[0], p2[1]);
 125           ctx.closePath();
 126           ctx.stroke();
 127           ctx.restore();
 128         }
 129       }
 130
 131     </script>
 132
 133     <div style="position: absolute; left: 500px; top: 150px;">
 134     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 135     <br/><br/>
 136     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 137     <br/><br/>
 138     <input type=button value="Clear Lines" onClick="clearLines()" />
 139     </div>
 140 </body>
 141 </html>