--- /dev/null
+/**
+ * @fileoverview Tests for the smooth (bezier curve) plotter.
+ *
+ * @author danvdk@gmail.com (Dan Vanderkam)
+ */
+var smoothPlotterTestCase = TestCase("smooth-plotter");
+
+var getControlPoints = smoothPlotter._getControlPoints;
+
+smoothPlotterTestCase.prototype.setUp = function() {
+};
+
+smoothPlotterTestCase.prototype.tearDown = function() {
+};
+
+smoothPlotterTestCase.prototype.testNoSmoothing = function() {
+ var lastPt = {x: 10, y: 0},
+ pt = {x: 11, y: 1},
+ nextPt = {x: 12, y: 0},
+ alpha = 0;
+
+ assertEquals([11, 1, 11, 1], getControlPoints(lastPt, pt, nextPt, alpha));
+};
+
+smoothPlotterTestCase.prototype.testHalfSmoothing = function() {
+ var lastPt = {x: 10, y: 0},
+ pt = {x: 11, y: 1},
+ nextPt = {x: 12, y: 0},
+ alpha = 0.5;
+
+ assertEquals([10.5, 1, 11.5, 1], getControlPoints(lastPt, pt, nextPt, alpha));
+}
+
+smoothPlotterTestCase.prototype.testExtrema = function() {
+ var lastPt = {x: 10, y: 0},
+ pt = {x: 11, y: 1},
+ nextPt = {x: 12, y: 1},
+ alpha = 0.5;
+
+ assertEquals([10.5, 0.75, 11.5, 1.25],
+ getControlPoints(lastPt, pt, nextPt, alpha, true));
+
+ assertEquals([10.5, 1, 11.5, 1],
+ getControlPoints(lastPt, pt, nextPt, alpha, false));
+}
--- /dev/null
+var smoothPlotter = (function() {
+"use strict";
+
+/**
+ * Given three sequential points, p0, p1 and p2, find the left and right
+ * control points for p1.
+ *
+ * The three points are expected to have x and y properties.
+ *
+ * The alpha parameter controls the amount of smoothing.
+ * If α=0, then both control points will be the same as p1 (i.e. no smoothing).
+ *
+ * Returns [l1x, l1y, r1x, r1y]
+ *
+ * It's guaranteed that the line from (l1x, l1y)-(r1x, r1y) passes through p1.
+ * Unless allowFalseExtrema is set, then it's also guaranteed that:
+ * l1y ∈ [p0.y, p1.y]
+ * r1y ∈ [p1.y, p2.y]
+ *
+ * The basic algorithm is:
+ * 1. Put the control points l1 and r1 α of the way down (p0, p1) and (p1, p2).
+ * 2. Shift l1 and r2 so that the line l1–r1 passes through p1
+ * 3. Adjust to prevent false extrema while keeping p1 on the l1–r1 line.
+ *
+ * This is loosely based on the HighCharts algorithm.
+ */
+function getControlPoints(p0, p1, p2, opt_alpha, opt_allowFalseExtrema) {
+ var alpha = (opt_alpha !== undefined) ? opt_alpha : 1/3; // 0=no smoothing, 1=crazy smoothing
+ var allowFalseExtrema = opt_allowFalseExtrema || false;
+
+ if (!p2) {
+ return [p1.x, p1.y, null, null];
+ }
+
+ // Step 1: Position the control points along each line segment.
+ var l1x = (1 - alpha) * p1.x + alpha * p0.x,
+ l1y = (1 - alpha) * p1.y + alpha * p0.y,
+ r1x = (1 - alpha) * p1.x + alpha * p2.x,
+ r1y = (1 - alpha) * p1.y + alpha * p2.y;
+
+ // Step 2: shift the points up so that p1 is on the l1–r1 line.
+ if (l1x != r1x) {
+ // This can be derived w/ some basic algebra.
+ var deltaY = p1.y - r1y - (p1.x - r1x) * (l1y - r1y) / (l1x - r1x);
+ l1y += deltaY;
+ r1y += deltaY;
+ }
+
+ // Step 3: correct to avoid false extrema.
+ if (!allowFalseExtrema) {
+ if (l1y > p0.y && l1y > p1.y) {
+ l1y = Math.max(p0.y, p1.y);
+ r1y = 2 * p1.y - l1y;
+ } else if (l1y < p0.y && l1y < p1.y) {
+ l1y = Math.min(p0.y, p1.y);
+ r1y = 2 * p1.y - l1y;
+ }
+
+ if (r1y > p1.y && r1y > p2.y) {
+ r1y = Math.max(p1.y, p2.y);
+ l1y = 2 * p1.y - r1y;
+ } else if (r1y < p1.y && r1y < p2.y) {
+ r1y = Math.min(p1.y, p2.y);
+ l1y = 2 * p1.y - r1y;
+ }
+ }
+
+ return [l1x, l1y, r1x, r1y];
+}
+
+
+// A plotter which uses splines to create a smooth curve.
+// See tests/plotters.html for a demo.
+// Can be controlled via smoothPlotter.smoothing
+function smoothPlotter(e) {
+ var ctx = e.drawingContext,
+ points = e.points;
+
+ ctx.beginPath();
+ ctx.moveTo(points[0].canvasx, points[0].canvasy);
+
+ // right control point for previous point
+ var lastRightX = points[0].canvasx, lastRightY = points[0].canvasy;
+ var isOK = Dygraph.isOK; // i.e. is none of (null, undefined, NaN)
+
+ for (var i = 1; i < points.length; i++) {
+ var p0 = points[i - 1],
+ p1 = points[i],
+ p2 = points[i + 1];
+ p0 = p0 && isOK(p0.canvasy) ? p0 : null;
+ p1 = p1 && isOK(p1.canvasy) ? p1 : null;
+ p2 = p2 && isOK(p2.canvasy) ? p2 : null;
+ if (p0 && p1) {
+ var controls = getControlPoints({x: p0.canvasx, y: p0.canvasy},
+ {x: p1.canvasx, y: p1.canvasy},
+ p2 && {x: p2.canvasx, y: p2.canvasy},
+ smoothPlotter.smoothing);
+ // Uncomment to show the control points:
+ // ctx.lineTo(lastRightX, lastRightY);
+ // ctx.lineTo(controls[0], controls[1]);
+ // ctx.lineTo(p1.canvasx, p1.canvasy);
+ lastRightX = (lastRightX !== null) ? lastRightX : p0.canvasx;
+ lastRightY = (lastRightY !== null) ? lastRightY : p0.canvasy;
+ ctx.bezierCurveTo(lastRightX, lastRightY,
+ controls[0], controls[1],
+ p1.canvasx, p1.canvasy);
+ lastRightX = controls[2];
+ lastRightY = controls[3];
+ } else if (p1) {
+ // We're starting again after a missing point.
+ ctx.moveTo(p1.canvasx, p1.canvasy);
+ lastRightX = p1.canvasx;
+ lastRightY = p1.canvasy;
+ } else {
+ lastRightX = lastRightY = null;
+ }
+ }
+
+ ctx.stroke();
+}
+smoothPlotter.smoothing = 1/3;
+smoothPlotter._getControlPoints = getControlPoints; // for testing
+
+return smoothPlotter;
+
+})();
--- /dev/null
+<!DOCTYPE html>
+<html>
+ <head>
+ <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9">
+ <title>Plotters demo</title>
+ <!--[if IE]>
+ <script type="text/javascript" src="../excanvas.js"></script>
+ <![endif]-->
+ <script type="text/javascript" src="../dygraph-dev.js"></script>
+ <script type="text/javascript" src="../extras/smooth-plotter.js"></script>
+
+ <style type="text/css">
+ body {
+ max-width: 700px;
+ }
+ div.chart {
+ width: 640px;
+ height: 320px;
+ }
+ input[type="range"] {
+ width: 400px;
+ }
+ .smoother {
+ margin-left: 50px;
+ }
+ </style>
+ </head>
+ <body>
+ <h2>Smooth Lines</h2>
+ <p>This plotter draws smooth lines between points using bezier curves.</p>
+ <p class="smoother">Smoothing: <input type="range" id="smoothing-amount" min=0 max=0.7 step=0.01 value=0.33> <span id="smoothing-param">0.33</span></p>
+ <div id="smooth-line" class="chart"></div>
+
+ <p>View source to see how this works. You'll have to source <code>extras/smooth-plotter.js</code> in addition to dygraphs to get this feature. See the <a href="https://github.com/danvk/dygraphs/pull/469">pull request</a> that introduced this plotter to learn more about how it smooths your curves.</p>
+
+<script type="text/javascript">
+// Smooth line plotter
+var functionData = [];
+var vs = [10, 20, 40, 0, 30, 15, 25, 60, 35, 45];
+for (var i = 0; i < 10; i++) {
+ var v = vs[i];
+ functionData.push([i, v, v]);
+}
+
+var g6;
+function drawSmoothPlot() {
+ g6 = new Dygraph(document.getElementById('smooth-line'),
+ functionData,
+ {
+ labels: ['Year', 'Straight', 'Smoothed'],
+ series: {
+ Straight: {
+ color: 'rgba(0,0,0,0.33)',
+ strokeWidth: 2,
+ drawPoints: true,
+ pointSize: 3
+ },
+ Smoothed: {
+ plotter: smoothPlotter,
+ color: 'red',
+ strokeWidth: 2
+ }
+ },
+ legend: 'always',
+ gridLineColor: '#ddd'
+ });
+}
+drawSmoothPlot();
+
+var smoothRangeEl = document.getElementById('smoothing-amount');
+smoothRangeEl.addEventListener('input', function() {
+ var param = parseFloat(smoothRangeEl.value);
+ smoothPlotter.smoothing = param;
+ document.getElementById('smoothing-param').innerHTML = param;
+ drawSmoothPlot();
+});
+</script>
+</body>
+</html>
projects / dygraphs.git / commitdiff