tests/linear-regression.html

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