Only add 1 point per pixel for graphs without error bars to speed up rendering.

[dygraphs.git] / dygraph-layout.js

// Copyright 2011 Dan Vanderkam (danvdk@gmail.com)
// All Rights Reserved.

/**
 * @fileoverview Based on PlotKitLayout, but modified to meet the needs of
 * dygraphs.
 */

/**
 * Creates a new DygraphLayout object.
 *
 * This class contains all the data to be charted.
 * It uses data coordinates, but also records the chart range (in data
 * coordinates) and hence is able to calculate percentage positions ('In this
 * view, Point A lies 25% down the x-axis.')
 *
 * Two things that it does not do are:
 * 1. Record pixel coordinates for anything.
 * 2. (oddly) determine anything about the layout of chart elements.
 *
 * The naming is a vestige of Dygraph's original PlotKit roots.
 *
 * @constructor
 */
DygraphLayout = function(dygraph) {
  this.dygraph_ = dygraph;
  this.datasets = new Array();
  this.annotations = new Array();
  this.yAxes_ = null;

  // TODO(danvk): it's odd that xTicks_ and yTicks_ are inputs, but xticks and
  // yticks are outputs. Clean this up.
  this.xTicks_ = null;
  this.yTicks_ = null;
};

DygraphLayout.prototype.attr_ = function(name) {
  return this.dygraph_.attr_(name);
};

DygraphLayout.prototype.addDataset = function(setname, set_xy) {
  this.datasets[setname] = set_xy;
};

DygraphLayout.prototype.setAnnotations = function(ann) {
  // The Dygraph object's annotations aren't parsed. We parse them here and
  // save a copy. If there is no parser, then the user must be using raw format.
  this.annotations = [];
  var parse = this.attr_('xValueParser') || function(x) { return x; };
  for (var i = 0; i < ann.length; i++) {
    var a = {};
    if (!ann[i].xval && !ann[i].x) {
      this.dygraph_.error("Annotations must have an 'x' property");
      return;
    }
    if (ann[i].icon &&
        !(ann[i].hasOwnProperty('width') &&
          ann[i].hasOwnProperty('height'))) {
      this.dygraph_.error("Must set width and height when setting " +
                          "annotation.icon property");
      return;
    }
    Dygraph.update(a, ann[i]);
    if (!a.xval) a.xval = parse(a.x);
    this.annotations.push(a);
  }
};

DygraphLayout.prototype.setXTicks = function(xTicks) {
  this.xTicks_ = xTicks;
};

// TODO(danvk): add this to the Dygraph object's API or move it into Layout.
DygraphLayout.prototype.setYAxes = function (yAxes) {
  this.yAxes_ = yAxes;
};

DygraphLayout.prototype.setDateWindow = function(dateWindow) {
  this.dateWindow_ = dateWindow;
};

DygraphLayout.prototype.evaluate = function() {
  this._evaluateLimits();
  this._evaluateLineCharts();
  this._evaluateLineTicks();
  this._evaluateAnnotations();
};

DygraphLayout.prototype._evaluateLimits = function() {
  this.minxval = this.maxxval = null;
  if (this.dateWindow_) {
    this.minxval = this.dateWindow_[0];
    this.maxxval = this.dateWindow_[1];
  } else {
    for (var name in this.datasets) {
      if (!this.datasets.hasOwnProperty(name)) continue;
      var series = this.datasets[name];
      if (series.length > 1) {
        var x1 = series[0][0];
        if (!this.minxval || x1 < this.minxval) this.minxval = x1;
  
        var x2 = series[series.length - 1][0];
        if (!this.maxxval || x2 > this.maxxval) this.maxxval = x2;
      }
    }
  }
  this.xrange = this.maxxval - this.minxval;
  this.xscale = (this.xrange != 0 ? 1/this.xrange : 1.0);

  for (var i = 0; i < this.yAxes_.length; i++) {
    var axis = this.yAxes_[i];
    axis.minyval = axis.computedValueRange[0];
    axis.maxyval = axis.computedValueRange[1];
    axis.yrange = axis.maxyval - axis.minyval;
    axis.yscale = (axis.yrange != 0 ? 1.0 / axis.yrange : 1.0);

    if (axis.g.attr_("logscale")) {
      axis.ylogrange = Dygraph.log10(axis.maxyval) - Dygraph.log10(axis.minyval);
      axis.ylogscale = (axis.ylogrange != 0 ? 1.0 / axis.ylogrange : 1.0);
      if (!isFinite(axis.ylogrange) || isNaN(axis.ylogrange)) {
        axis.g.error('axis ' + i + ' of graph at ' + axis.g +
            ' can\'t be displayed in log scale for range [' +
            axis.minyval + ' - ' + axis.maxyval + ']');
      }
    }
  }
};

DygraphLayout.prototype._evaluateLineCharts = function() {
  // add all the rects
  this.points = new Array();
  for (var setName in this.datasets) {
    if (!this.datasets.hasOwnProperty(setName)) continue;

    var dataset = this.datasets[setName];
    var axis = this.dygraph_.axisPropertiesForSeries(setName);

    var graphWidth = this.dygraph_.width_;
    var graphHeight = this.dygraph_.height_;
    var prevXPx = NaN;
    var prevYPx = NaN;
    var currXPx = NaN;
    var currYPx = NaN;
    
    var errorBars = this.attr_("errorBars") || this.attr_("customBars");

    for (var j = 0; j < dataset.length; j++) {
      var item = dataset[j];
      var xValue = parseFloat(dataset[j][0]);
      var yValue = parseFloat(dataset[j][1]);
      
      // Range from 0-1 where 0 represents top and 1 represents bottom
      var xNormal = (xValue - this.minxval) * this.xscale;
      // Range from 0-1 where 0 represents left and 1 represents right.
      var yNormal;
      if (axis.logscale) {
        yNormal = 1.0 - ((Dygraph.log10(yValue) - Dygraph.log10(axis.minyval)) * axis.ylogscale);
      } else {
        yNormal = 1.0 - ((yValue - axis.minyval) * axis.yscale);
      }
      
      // Current pixel coordinates that the data point would fill.
      currXPx = Math.round(xNormal * graphWidth);
      currYPx = Math.round(yNormal * graphHeight);

      // Skip over pushing points that lie on the same pixel.
      // Ignore this optimization if there are error bars.
      // TODO(antrob): optimize this for graphs with error bars.
      if (prevXPx != currXPx || prevYPx != currYPx || errorBars) {
        // TODO(antrob): skip over points that lie on a line that is already going to be drawn.
        // There is no need to have more than 2 consecutive points that are collinear.
        var point = {
          // TODO(danvk): here
          x: xNormal,
          y: yNormal,
          xval: xValue,
          yval: yValue,
          name: setName
        };
        this.points.push(point);
      }
      prevXPx = currXPx;
      prevYPx = currYPx;
    }
  }
};

DygraphLayout.prototype._evaluateLineTicks = function() {
  this.xticks = new Array();
  for (var i = 0; i < this.xTicks_.length; i++) {
    var tick = this.xTicks_[i];
    var label = tick.label;
    var pos = this.xscale * (tick.v - this.minxval);
    if ((pos >= 0.0) && (pos <= 1.0)) {
      this.xticks.push([pos, label]);
    }
  }

  this.yticks = new Array();
  for (var i = 0; i < this.yAxes_.length; i++ ) {
    var axis = this.yAxes_[i];
    for (var j = 0; j < axis.ticks.length; j++) {
      var tick = axis.ticks[j];
      var label = tick.label;
      var pos = this.dygraph_.toPercentYCoord(tick.v, i);
      if ((pos >= 0.0) && (pos <= 1.0)) {
        this.yticks.push([i, pos, label]);
      }
    }
  }
};


/**
 * Behaves the same way as PlotKit.Layout, but also copies the errors
 * @private
 */
DygraphLayout.prototype.evaluateWithError = function() {
  this.evaluate();
  if (!(this.attr_('errorBars') || this.attr_('customBars'))) return;

  // Copy over the error terms
  var i = 0; // index in this.points
  for (var setName in this.datasets) {
    if (!this.datasets.hasOwnProperty(setName)) continue;
    var j = 0;
    var dataset = this.datasets[setName];
    for (var j = 0; j < dataset.length; j++, i++) {
      var item = dataset[j];
      var xv = parseFloat(item[0]);
      var yv = parseFloat(item[1]);

      if (xv == this.points[i].xval &&
          yv == this.points[i].yval) {
        this.points[i].errorMinus = parseFloat(item[2]);
        this.points[i].errorPlus = parseFloat(item[3]);
      }
    }
  }
};

DygraphLayout.prototype._evaluateAnnotations = function() {
  // Add the annotations to the point to which they belong.
  // Make a map from (setName, xval) to annotation for quick lookups.
  var annotations = {};
  for (var i = 0; i < this.annotations.length; i++) {
    var a = this.annotations[i];
    annotations[a.xval + "," + a.series] = a;
  }

  this.annotated_points = [];

  // Exit the function early if there are no annotations.
  if (!this.annotations || !this.annotations.length) {
    return;
  }
  
  // TODO(antrob): loop through annotations not points.
  for (var i = 0; i < this.points.length; i++) {
    var p = this.points[i];
    var k = p.xval + "," + p.name;
    if (k in annotations) {
      p.annotation = annotations[k];
      this.annotated_points.push(p);
    }
  }
};

/**
 * Convenience function to remove all the data sets from a graph
 */
DygraphLayout.prototype.removeAllDatasets = function() {
  delete this.datasets;
  this.datasets = new Array();
};

/**
 * Return a copy of the point at the indicated index, with its yval unstacked.
 * @param int index of point in layout_.points
 */
DygraphLayout.prototype.unstackPointAtIndex = function(idx) {
  var point = this.points[idx];
  
  // Clone the point since we modify it
  var unstackedPoint = {};  
  for (var i in point) {
    unstackedPoint[i] = point[i];
  }
  
  if (!this.attr_("stackedGraph")) {
    return unstackedPoint;
  }
  
  // The unstacked yval is equal to the current yval minus the yval of the 
  // next point at the same xval.
  for (var i = idx+1; i < this.points.length; i++) {
    if (this.points[i].xval == point.xval) {
      unstackedPoint.yval -= this.points[i].yval; 
      break;
    }
  }
  
  return unstackedPoint;
}