--- /dev/null
+<html>
+ <head>
+ <title>Linear Regression</title>
+ <!--[if IE]>
+ <script type="text/javascript" src="excanvas.js"></script>
+ <![endif]-->
+ <script type="text/javascript" src="../strftime/strftime-min.js"></script>
+ <script type="text/javascript" src="../rgbcolor/rgbcolor.js"></script>
+ <script type="text/javascript" src="../dygraph-canvas.js"></script>
+ <script type="text/javascript" src="../dygraph.js"></script>
+ <style type="text/css">
+ body { max-width: 640 px; }
+ </style>
+ </head>
+ <body>
+ <h2>Linear Regression Demo</h2>
+ <p>Click the buttons to generate linear regressions over either data
+ series. If you zoom in and click the regression button, the regression will
+ only be run over visible points. Zoom back out to see what the local
+ regression looks like over the full data.</p>
+
+ <div id="demodiv" style="width: 480px; height: 320px;"></div>
+
+ <script type="text/javascript">
+ var data = [];
+ for (var i = 0; i < 120; i++) {
+ data.push([i,
+ i / 5.0 + 10.0 * Math.sin(i / 3.0),
+ 30.0 - i / 5.0 - 10.0 * Math.sin(i / 3.0 + 1.0)]);
+ }
+
+ g = new Dygraph(
+ document.getElementById("demodiv"),
+ data,
+ {
+ labels: ['X', 'Y1', 'Y2'],
+ underlayCallback: drawLines,
+ drawPoints: true
+ }
+ );
+
+ // coefficients of regression for each series.
+ // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1
+ // only. The regression line is y = 1 + 2 * x.
+ var coeffs = [ null, null, null ];
+ function regression(series) {
+ // Only run the regression over visible points.
+ var range = g.xAxisRange();
+
+ var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0;
+ for (var i = 0; i < g.numRows(); i++) {
+ var x = g.getValue(i, 0);
+ if (x < range[0] || x > range[1]) continue;
+
+ var y = g.getValue(i, series);
+ if (y == null) continue;
+
+ num++;
+ sum_x += x;
+ sum_y += y;
+ sum_xy += x * y;
+ sum_x2 += x * x;
+ }
+
+ var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num);
+ var b = (sum_y - a * sum_x) / num;
+
+ coeffs[series] = [b, a];
+ console.log("coeffs(" + series + "): [" + b + ", " + a + "]");
+
+ g.updateOptions({}); // forces a redraw.
+ }
+
+ function clearLines() {
+ for (var i = 0; i < coeffs.length; i++) coeffs[i] = null;
+ g.updateOptions({});
+ }
+
+ function drawLines(ctx, area, layout) {
+ if (typeof(g) == 'undefined') return; // won't be set on the initial draw.
+
+ var range = g.xAxisRange();
+ for (var i = 0; i < coeffs.length; i++) {
+ if (!coeffs[i]) continue;
+ var a = coeffs[i][1];
+ var b = coeffs[i][0];
+
+ var x1 = range[0];
+ var y1 = a * x1 + b;
+ var x2 = range[1];
+ var y2 = a * x2 + b;
+
+ var p1 = g.toDomCoords(x1, y1);
+ var p2 = g.toDomCoords(x2, y2);
+
+ console.log("(" + x1 + ", " + y1 + ") - (" + x2 + ", " + y2 + ")");
+ var color = g.getColors()[i - 1];
+ ctx.save();
+ ctx.strokeStyle = color;
+ ctx.lineWidth = 1.0;
+ ctx.beginPath();
+ ctx.moveTo(p1[0], p1[1]);
+ ctx.lineTo(p2[0], p2[1]);
+ ctx.closePath();
+ ctx.stroke();
+ ctx.restore();
+ }
+ }
+
+ </script>
+
+ <div style="position: absolute; left: 500px; top: 150px;">
+ <input type=button style="color: green;" value="Regression (Y1)" onClick="regression(1)" />
+ <br/><br/>
+ <input type=button style="color: blue;" value="Regression (Y2)" onClick="regression(2)" />
+ <br/><br/>
+ <input type=button value="Clear Lines" onClick="clearLines()" />
+ </div>
+</body>
+</html>
projects / dygraphs.git / commitdiff