dygraph-canvas.js

   1 // Copyright 2006 Dan Vanderkam (danvdk@gmail.com)
   2 // All Rights Reserved.
   3
   4 /**
   5  * @fileoverview Subclasses various parts of PlotKit to meet the additional
   6  * needs of Dygraph: grid overlays and error bars
   7  */
   8
   9 // Subclass PlotKit.Layout to add:
  10 // 1. Sigma/errorBars properties
  11 // 2. Copy error terms for PlotKit.CanvasRenderer._renderLineChart
  12
  13 /**
  14  * Creates a new DygraphLayout object. Options are the same as those allowed
  15  * by the PlotKit.Layout constructor.
  16  * @param {Object} options Options for PlotKit.Layout
  17  * @return {Object} The DygraphLayout object
  18  */
  19 DygraphLayout = function(options) {
  20   PlotKit.Layout.call(this, "line", options);
  21 };
  22 DygraphLayout.prototype = new PlotKit.Layout();
  23
  24 /**
  25  * Behaves the same way as PlotKit.Layout, but also copies the errors
  26  * @private
  27  */
  28 DygraphLayout.prototype.evaluateWithError = function() {
  29   this.evaluate();
  30   if (!this.options.errorBars) return;
  31
  32   // Copy over the error terms
  33   var i = 0; // index in this.points
  34   for (var setName in this.datasets) {
  35     var j = 0;
  36     var dataset = this.datasets[setName];
  37     if (PlotKit.Base.isFuncLike(dataset)) continue;
  38     for (var j = 0; j < dataset.length; j++, i++) {
  39       var item = dataset[j];
  40       var xv = parseFloat(item[0]);
  41       var yv = parseFloat(item[1]);
  42
  43       if (xv == this.points[i].xval &&
  44           yv == this.points[i].yval) {
  45         this.points[i].errorMinus = parseFloat(item[2]);
  46         this.points[i].errorPlus = parseFloat(item[3]);
  47       }
  48     }
  49   }
  50 };
  51
  52 /**
  53  * Convenience function to remove all the data sets from a graph
  54  */
  55 DygraphLayout.prototype.removeAllDatasets = function() {
  56   delete this.datasets;
  57   this.datasets = new Array();
  58 };
  59
  60 /**
  61  * Change the values of various layout options
  62  * @param {Object} new_options an associative array of new properties
  63  */
  64 DygraphLayout.prototype.updateOptions = function(new_options) {
  65   MochiKit.Base.update(this.options, new_options ? new_options : {});
  66 };
  67
  68 // Subclass PlotKit.CanvasRenderer to add:
  69 // 1. X/Y grid overlay
  70 // 2. Ability to draw error bars (if required)
  71
  72 /**
  73  * Sets some PlotKit.CanvasRenderer options
  74  * @param {Object} element The canvas to attach to
  75  * @param {Layout} layout The DygraphLayout object for this graph.
  76  * @param {Object} options Options to pass on to CanvasRenderer
  77  */
  78 DygraphCanvasRenderer = function(element, layout, options) {
  79   PlotKit.CanvasRenderer.call(this, element, layout, options);
  80   this.options.shouldFill = false;
  81   this.options.shouldStroke = true;
  82   this.options.drawYGrid = true;
  83   this.options.drawXGrid = true;
  84   this.options.gridLineColor = MochiKit.Color.Color.grayColor();
  85   MochiKit.Base.update(this.options, options);
  86
  87   // TODO(danvk) This shouldn't be necessary: effects should be overlaid
  88   this.options.drawBackground = false;
  89 };
  90 DygraphCanvasRenderer.prototype = new PlotKit.CanvasRenderer();
  91
  92 /**
  93  * Draw an X/Y grid on top of the existing plot
  94  */
  95 DygraphCanvasRenderer.prototype.render = function() {
  96   // Draw the new X/Y grid
  97   var ctx = this.element.getContext("2d");
  98   if (this.options.drawYGrid) {
  99     var ticks = this.layout.yticks;
 100     ctx.save();
 101     ctx.strokeStyle = this.options.gridLineColor.toRGBString();
 102     ctx.lineWidth = this.options.axisLineWidth;
 103     for (var i = 0; i < ticks.length; i++) {
 104       var x = this.area.x;
 105       var y = this.area.y + ticks[i][0] * this.area.h;
 106       ctx.beginPath();
 107       ctx.moveTo(x, y);
 108       ctx.lineTo(x + this.area.w, y);
 109       ctx.closePath();
 110       ctx.stroke();
 111     }
 112   }
 113
 114   if (this.options.drawXGrid) {
 115     var ticks = this.layout.xticks;
 116     ctx.save();
 117     ctx.strokeStyle = this.options.gridLineColor.toRGBString();
 118     ctx.lineWidth = this.options.axisLineWidth;
 119     for (var i=0; i<ticks.length; i++) {
 120       var x = this.area.x + ticks[i][0] * this.area.w;
 121       var y = this.area.y + this.area.h;
 122       ctx.beginPath();
 123       ctx.moveTo(x, y);
 124       ctx.lineTo(x, this.area.y);
 125       ctx.closePath();
 126       ctx.stroke();
 127     }
 128   }
 129
 130   // Do the ordinary rendering, as before
 131   // TODO(danvk) Call super.render()
 132   this._renderLineChart();
 133   this._renderLineAxis();
 134 };
 135
 136 /**
 137  * Overrides the CanvasRenderer method to draw error bars
 138  */
 139 DygraphCanvasRenderer.prototype._renderLineChart = function() {
 140   var context = this.element.getContext("2d");
 141   var colorCount = this.options.colorScheme.length;
 142   var colorScheme = this.options.colorScheme;
 143   var setNames = MochiKit.Base.keys(this.layout.datasets);
 144   var errorBars = this.layout.options.errorBars;
 145   var setCount = setNames.length;
 146   var bind = MochiKit.Base.bind;
 147   var partial = MochiKit.Base.partial;
 148
 149   //Update Points
 150   var updatePoint = function(point) {
 151     point.canvasx = this.area.w * point.x + this.area.x;
 152     point.canvasy = this.area.h * point.y + this.area.y;
 153   }
 154   MochiKit.Iter.forEach(this.layout.points, updatePoint, this);
 155
 156   // create paths
 157   var makePath = function(ctx) {
 158     for (var i = 0; i < setCount; i++) {
 159       var setName = setNames[i];
 160       var color = colorScheme[i%colorCount];
 161       var strokeX = this.options.strokeColorTransform;
 162
 163       // setup graphics context
 164       context.save();
 165       context.strokeStyle = color.toRGBString();
 166       context.lineWidth = this.options.strokeWidth;
 167       ctx.beginPath();
 168       var point = this.layout.points[0];
 169       var first_point = true;
 170       var addPoint = function(ctx_, point) {
 171         if (point.name == setName) {
 172           if (!point.canvasy || isNaN(point.canvasy)) {
 173             // this will make us move to the next point, not draw a line to it.
 174             first_point = true;
 175           } else {
 176             if (first_point) {
 177               ctx_.moveTo(point.canvasx, point.canvasy);
 178               first_point = false;
 179             } else {
 180               ctx_.lineTo(point.canvasx, point.canvasy);
 181             }
 182           }
 183         }
 184       };
 185       MochiKit.Iter.forEach(this.layout.points, partial(addPoint, ctx), this);
 186       ctx.stroke();
 187     }
 188   };
 189
 190   var makeErrorBars = function(ctx) {
 191     for (var i = 0; i < setCount; i++) {
 192       var setName = setNames[i];
 193       var color = colorScheme[i % colorCount];
 194       var strokeX = this.options.strokeColorTransform;
 195
 196       // setup graphics context
 197       context.save();
 198       context.strokeStyle = color.toRGBString();
 199       context.lineWidth = this.options.strokeWidth;
 200       var prevX = -1;
 201       var prevYs = [-1, -1];
 202       var count = 0;
 203       var yscale = this.layout.yscale;
 204       var errorTrapezoid = function(ctx_,point) {
 205         count++;
 206         if (point.name == setName) {
 207           if (!point.y || isNaN(point.y)) {
 208             prevX = -1;
 209             return;
 210           }
 211           var newYs = [ point.y - point.errorPlus * yscale,
 212                         point.y + point.errorMinus * yscale ];
 213           newYs[0] = this.area.h * newYs[0] + this.area.y;
 214           newYs[1] = this.area.h * newYs[1] + this.area.y;
 215           if (prevX >= 0) {
 216             ctx_.moveTo(prevX, prevYs[0]);
 217             ctx_.lineTo(point.canvasx, newYs[0]);
 218             ctx_.lineTo(point.canvasx, newYs[1]);
 219             ctx_.lineTo(prevX, prevYs[1]);
 220             ctx_.closePath();
 221           }
 222           prevYs[0] = newYs[0];
 223           prevYs[1] = newYs[1];
 224           prevX = point.canvasx;
 225         }
 226       };
 227       // should be same color as the lines
 228       var err_color = color.colorWithAlpha(0.15);
 229       ctx.fillStyle = err_color.toRGBString();
 230       ctx.beginPath();
 231       MochiKit.Iter.forEach(this.layout.points, partial(errorTrapezoid, ctx), this);
 232       ctx.fill();
 233     }
 234   };
 235
 236   if (errorBars)
 237     bind(makeErrorBars, this)(context);
 238   bind(makePath, this)(context);
 239   context.restore();
 240 };