| 1 | // Use this as a template for new Gallery entries. |
| 2 | Gallery.register( |
| 3 | 'linear-regression', |
| 4 | { |
| 5 | name: 'Linear Regressions', |
| 6 | title: 'Linear Regression Demo', |
| 7 | setup: function(parent) { |
| 8 | parent.innerHTML = |
| 9 | "<p>Click the buttons to generate linear regressions over either data "+ |
| 10 | "series. If you zoom in and then click the regression button, the regression "+ |
| 11 | "will only be run over visible points. Zoom back out to see what the local "+ |
| 12 | "regression looks like over the full data.</p> "+ |
| 13 | "<div id='demodiv' style='width: 480px; height: 320px;'></div>" + |
| 14 | "<div style='text-align:center; width: 480px'>" + |
| 15 | "<button style='color: green;' id='ry1'>Regression (Y1)</button> " + |
| 16 | "<button style='color: blue;' id='ry2'>Regression (Y2)</button> " + |
| 17 | "<button id='clear'>Clear Lines</button>" + |
| 18 | "</div>"; |
| 19 | }, |
| 20 | run: function() { |
| 21 | document.getElementById("ry1").onclick = function() { regression(1) }; |
| 22 | document.getElementById("ry2").onclick = function() { regression(2) }; |
| 23 | document.getElementById("clear").onclick = function() { clearLines() }; |
| 24 | |
| 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 | // coefficients of regression for each series. |
| 33 | // if coeffs = [ null, [1, 2], null ] then we draw a regression for series 1 |
| 34 | // only. The regression line is y = 1 + 2 * x. |
| 35 | var coeffs = [ null, null, null ]; |
| 36 | function regression(series) { |
| 37 | // Only run the regression over visible points. |
| 38 | var range = g.xAxisRange(); |
| 39 | |
| 40 | var sum_xy = 0.0, sum_x = 0.0, sum_y = 0.0, sum_x2 = 0.0, num = 0; |
| 41 | for (var i = 0; i < g.numRows(); i++) { |
| 42 | var x = g.getValue(i, 0); |
| 43 | if (x < range[0] || x > range[1]) continue; |
| 44 | |
| 45 | var y = g.getValue(i, series); |
| 46 | if (y == null) continue; |
| 47 | if (y.length == 2) { |
| 48 | // using fractions |
| 49 | y = y[0] / y[1]; |
| 50 | } |
| 51 | |
| 52 | num++; |
| 53 | sum_x += x; |
| 54 | sum_y += y; |
| 55 | sum_xy += x * y; |
| 56 | sum_x2 += x * x; |
| 57 | } |
| 58 | |
| 59 | var a = (sum_xy - sum_x * sum_y / num) / (sum_x2 - sum_x * sum_x / num); |
| 60 | var b = (sum_y - a * sum_x) / num; |
| 61 | |
| 62 | coeffs[series] = [b, a]; |
| 63 | if (typeof(console) != 'undefined') { |
| 64 | console.log("coeffs(" + series + "): [" + b + ", " + a + "]"); |
| 65 | } |
| 66 | |
| 67 | g.updateOptions({}); // forces a redraw. |
| 68 | } |
| 69 | |
| 70 | function clearLines() { |
| 71 | for (var i = 0; i < coeffs.length; i++) coeffs[i] = null; |
| 72 | g.updateOptions({}); |
| 73 | } |
| 74 | |
| 75 | function drawLines(ctx, area, layout) { |
| 76 | if (typeof(g) == 'undefined') return; // won't be set on the initial draw. |
| 77 | |
| 78 | var range = g.xAxisRange(); |
| 79 | for (var i = 0; i < coeffs.length; i++) { |
| 80 | if (!coeffs[i]) continue; |
| 81 | var a = coeffs[i][1]; |
| 82 | var b = coeffs[i][0]; |
| 83 | |
| 84 | var x1 = range[0]; |
| 85 | var y1 = a * x1 + b; |
| 86 | var x2 = range[1]; |
| 87 | var y2 = a * x2 + b; |
| 88 | |
| 89 | var p1 = g.toDomCoords(x1, y1); |
| 90 | var p2 = g.toDomCoords(x2, y2); |
| 91 | |
| 92 | var c = new RGBColor(g.getColors()[i - 1]); |
| 93 | c.r = Math.floor(255 - 0.5 * (255 - c.r)); |
| 94 | c.g = Math.floor(255 - 0.5 * (255 - c.g)); |
| 95 | c.b = Math.floor(255 - 0.5 * (255 - c.b)); |
| 96 | var color = c.toHex(); |
| 97 | ctx.save(); |
| 98 | ctx.strokeStyle = color; |
| 99 | ctx.lineWidth = 1.0; |
| 100 | ctx.beginPath(); |
| 101 | ctx.moveTo(p1[0], p1[1]); |
| 102 | ctx.lineTo(p2[0], p2[1]); |
| 103 | ctx.closePath(); |
| 104 | ctx.stroke(); |
| 105 | ctx.restore(); |
| 106 | } |
| 107 | } |
| 108 | |
| 109 | g = new Dygraph( |
| 110 | document.getElementById("demodiv"), |
| 111 | data, |
| 112 | { |
| 113 | labels: ['X', 'Y1', 'Y2'], |
| 114 | underlayCallback: drawLines, |
| 115 | drawPoints: true, |
| 116 | strokeWidth: 0.0 |
| 117 | } |
| 118 | ); |
| 119 | } |
| 120 | }); |