tests/linear-regression.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 = [];
  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       }
  31
  32       g = new Dygraph(
  33               document.getElementById("demodiv"),
  34               data,
  35               {
  36                 labels: ['X', 'Y1', 'Y2'],
  37                 underlayCallback: drawLines,
  38                 drawPoints: true,
  39                 strokeWidth: 0.0
  40               }
  41           );
  42
  43       // coefficients of regression for each series.
  44       // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
  45       // only. The regression line is y = 1 + 2 * x.
  46       var coeffs = [ null, null, null ];
  47       function regression(series) {
  48         // Only run the regression over visible points.
  49         var range = g.xAxisRange();
  50
  51         var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
  52         for (var i = 0; i < g.numRows(); i++) {
  53           var x = g.getValue(i, 0);
  54           if (x < range[0] || x > range[1]) continue;
  55
  56           var y = g.getValue(i, series);
  57           if (y == null) continue;
  58
  59           num++;
  60           sum_x += x;
  61           sum_y += y;
  62           sum_xy += x * y;
  63           sum_x2 += x * x;
  64         }
  65
  66         var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
  67         var b = (sum_y - a * sum_x) / num;
  68
  69         coeffs[series] = [b, a];
  70         if (console) {
  71           console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
  72         }
  73
  74         g.updateOptions({});  // forces a redraw.
  75       }
  76
  77       function clearLines() {
  78         for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
  79         g.updateOptions({});
  80       }
  81
  82       function drawLines(ctx, area, layout) {
  83         if (typeof(g) == 'undefined') return;  // won't be set on the initial draw.
  84
  85         var range = g.xAxisRange();
  86         for (var i = 0; i < coeffs.length; i++) {
  87           if (!coeffs[i]) continue;
  88           var a = coeffs[i][1];
  89           var b = coeffs[i][0];
  90
  91           var x1 = range[0];
  92           var y1 = a * x1 + b;
  93           var x2 = range[1];
  94           var y2 = a * x2 + b;
  95
  96           var p1 = g.toDomCoords(x1, y1);
  97           var p2 = g.toDomCoords(x2, y2);
  98
  99           var c = new RGBColor(g.getColors()[i - 1]);
 100           c.r = Math.floor(255 - 0.5 * (255 - c.r));
 101           c.g = Math.floor(255 - 0.5 * (255 - c.g));
 102           c.b = Math.floor(255 - 0.5 * (255 - c.b));
 103           var color = c.toHex();
 104           ctx.save();
 105           ctx.strokeStyle = color;
 106           ctx.lineWidth = 1.0;
 107           ctx.beginPath();
 108           ctx.moveTo(p1[0], p1[1]);
 109           ctx.lineTo(p2[0], p2[1]);
 110           ctx.closePath();
 111           ctx.stroke();
 112           ctx.restore();
 113         }
 114       }
 115
 116     </script>
 117
 118     <div style="position: absolute; left: 500px; top: 150px;">
 119     <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
 120     <br/><br/>
 121     <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
 122     <br/><br/>
 123     <input type=button value="Clear Lines" onClick="clearLines()" />
 124     </div>
 125 </body>
 126 </html>