6 Dygraph = window.Dygraph;
7 } else if (typeof(module) !== 'undefined') {
8 Dygraph = require('../dygraph');
12 * Given three sequential points, p0, p1 and p2, find the left and right
13 * control points for p1.
15 * The three points are expected to have x and y properties.
17 * The alpha parameter controls the amount of smoothing.
18 * If α=0, then both control points will be the same as p1 (i.e. no smoothing).
20 * Returns [l1x, l1y, r1x, r1y]
22 * It's guaranteed that the line from (l1x, l1y)-(r1x, r1y) passes through p1.
23 * Unless allowFalseExtrema is set, then it's also guaranteed that:
27 * The basic algorithm is:
28 * 1. Put the control points l1 and r1 α of the way down (p0, p1) and (p1, p2).
29 * 2. Shift l1 and r2 so that the line l1–r1 passes through p1
30 * 3. Adjust to prevent false extrema while keeping p1 on the l1–r1 line.
32 * This is loosely based on the HighCharts algorithm.
34 function getControlPoints(p0, p1, p2, opt_alpha, opt_allowFalseExtrema) {
35 var alpha = (opt_alpha !== undefined) ? opt_alpha : 1/3; // 0=no smoothing, 1=crazy smoothing
36 var allowFalseExtrema = opt_allowFalseExtrema || false;
39 return [p1.x, p1.y, null, null];
42 // Step 1: Position the control points along each line segment.
43 var l1x = (1 - alpha) * p1.x + alpha * p0.x,
44 l1y = (1 - alpha) * p1.y + alpha * p0.y,
45 r1x = (1 - alpha) * p1.x + alpha * p2.x,
46 r1y = (1 - alpha) * p1.y + alpha * p2.y;
48 // Step 2: shift the points up so that p1 is on the l1–r1 line.
50 // This can be derived w/ some basic algebra.
51 var deltaY = p1.y - r1y - (p1.x - r1x) * (l1y - r1y) / (l1x - r1x);
56 // Step 3: correct to avoid false extrema.
57 if (!allowFalseExtrema) {
58 if (l1y > p0.y && l1y > p1.y) {
59 l1y = Math.max(p0.y, p1.y);
61 } else if (l1y < p0.y && l1y < p1.y) {
62 l1y = Math.min(p0.y, p1.y);
66 if (r1y > p1.y && r1y > p2.y) {
67 r1y = Math.max(p1.y, p2.y);
69 } else if (r1y < p1.y && r1y < p2.y) {
70 r1y = Math.min(p1.y, p2.y);
75 return [l1x, l1y, r1x, r1y];
78 // i.e. is none of (null, undefined, NaN)
80 return !!x && !isNaN(x);
83 // A plotter which uses splines to create a smooth curve.
84 // See tests/plotters.html for a demo.
85 // Can be controlled via smoothPlotter.smoothing
86 function smoothPlotter(e) {
87 var ctx = e.drawingContext,
91 ctx.moveTo(points[0].canvasx, points[0].canvasy);
93 // right control point for previous point
94 var lastRightX = points[0].canvasx, lastRightY = points[0].canvasy;
96 for (var i = 1; i < points.length; i++) {
97 var p0 = points[i - 1],
100 p0 = p0 && isOK(p0.canvasy) ? p0 : null;
101 p1 = p1 && isOK(p1.canvasy) ? p1 : null;
102 p2 = p2 && isOK(p2.canvasy) ? p2 : null;
104 var controls = getControlPoints({x: p0.canvasx, y: p0.canvasy},
105 {x: p1.canvasx, y: p1.canvasy},
106 p2 && {x: p2.canvasx, y: p2.canvasy},
107 smoothPlotter.smoothing);
108 // Uncomment to show the control points:
109 // ctx.lineTo(lastRightX, lastRightY);
110 // ctx.lineTo(controls[0], controls[1]);
111 // ctx.lineTo(p1.canvasx, p1.canvasy);
112 lastRightX = (lastRightX !== null) ? lastRightX : p0.canvasx;
113 lastRightY = (lastRightY !== null) ? lastRightY : p0.canvasy;
114 ctx.bezierCurveTo(lastRightX, lastRightY,
115 controls[0], controls[1],
116 p1.canvasx, p1.canvasy);
117 lastRightX = controls[2];
118 lastRightY = controls[3];
120 // We're starting again after a missing point.
121 ctx.moveTo(p1.canvasx, p1.canvasy);
122 lastRightX = p1.canvasx;
123 lastRightY = p1.canvasy;
125 lastRightX = lastRightY = null;
131 smoothPlotter.smoothing = 1/3;
132 smoothPlotter._getControlPoints = getControlPoints; // for testing
134 // older versions exported a global.
135 // This will be removed in the future.
136 // The preferred way to access smoothPlotter is via Dygraph.smoothPlotter.
137 window.smoothPlotter = smoothPlotter;
138 Dygraph.smoothPlotter = smoothPlotter;