code: function TimeseriesHistogram( graph ) {
  
  	var binHeight = 0;
  
  	// INSTANCE ATTRIBUTES //
  
  	this._parent = graph;
  	this._root = undefined;
  	this._children = {};
  	this._config = {
  		'type': 'timeseries-histogram',
  		'labels': []
  	};
  
  	// DATA //
  
  	this._data = graph._data;
  
  	// TRANSFORMS //
  
  	binHeight = graph._yScale( 0 ) - graph._yScale( 1 );
  
  	this._transforms = {
  		'x': function X( d ) {
  			return graph._xScale( d[ 0 ] );
  		},
  		'y': function Y( d, i ) {
  			return graph._yScale( i ) - binHeight;
  		},
  		'width': function Width( d ) {
  			return graph._xScale( d[ 2 ] ) - graph._xScale( d[ 0 ]);
  		},
  		'height': binHeight,
  		'color': function Color( d ) {
  			return graph._zScale( d[ 1 ] );
  		}
  	};
  
  	// REGISTER //
  	if ( graph._config.hasOwnProperty( 'marks' ) ) {
  		graph._config.marks.push( this._config );
  	} else {
  		graph._config.marks = [ this._config ];
  	}
  	if ( graph._children.hasOwnProperty( 'marks' ) ) {
  		graph._children.marks.push( this );
  	} else {
  		graph._children.marks = [ this ];
  	}
  
  	return this;
  
  }
docs: TIMESERIES HISTOGRAM // 
  FUNCTION: TimeseriesHistogram( graph )
  Timeseries histogram constructor. Creates a new timeseries histogram instance.
  
  @constructor
  @param {object} graph - parent graph instance
  @returns {object} timeseries histogram instance