tests/linear-regression.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     <script type="text/javascript" src="../strftime/strftime-min.js"></script>
  10     <script type="text/javascript" src="../rgbcolor/rgbcolor.js"></script>
  11     <script type="text/javascript" src="../dygraph-canvas.js"></script>
  12     <script type="text/javascript" src="../dygraph.js"></script>
  13     <style type="text/css">
  14     body { max-width: 640 px; }
  15     </style>
  16   </head>
  17   <body>
  18     <h2>Linear Regression Demo</h2>
  19     <p>Click the buttons to generate linear regressions over either data
  20     series. If you zoom in and click the regression button, the regression will
  21     only be run over visible points. Zoom back out to see what the local
  22     regression looks like over the full data.</p>
  23
  24     <div id="demodiv" style="width: 480px; height: 320px;"></div>
  25
  26     <script type="text/javascript">
  27       var data = [];
  28       for (var i = 0; i < 120; i++) {
  29         data.push([i,
  30                    i / 5.0 + 10.0 * Math.sin(i / 3.0),
  31                    30.0 - i / 5.0 - 10.0 * Math.sin(i / 3.0 + 1.0)]);
  32       }
  33
  34       g = new Dygraph(
  35               document.getElementById("demodiv"),
  36               data,
  37               {
  38                 labels: ['X', 'Y1', 'Y2'],
  39                 underlayCallback: drawLines,
  40                 drawPoints: true,
  41                 strokeWidth: 0.0
  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           var p1 = g.toDomCoords(x1, y1);
 103           var p2 = g.toDomCoords(x2, y2);
 104
 105           var c = new RGBColor(g.getColors()[i - 1]);
 106           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 107           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 108           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 109           var color = c.toHex();
 110           ctx.save();
 111           ctx.strokeStyle = color;
 112           ctx.lineWidth = 1.0;
 113           ctx.beginPath();
 114           ctx.moveTo(p1[0], p1[1]);
 115           ctx.lineTo(p2[0], p2[1]);
 116           ctx.closePath();
 117           ctx.stroke();
 118           ctx.restore();
 119         }
 120       }
 121
 122     </script>
 123
 124     <div style="position: absolute; left: 500px; top: 150px;">
 125     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 126     <br/><br/>
 127     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 128     <br/><br/>
 129     <input type=button value="Clear Lines" onClick="clearLines()" />
 130     </div>
 131 </body>
 132 </html>