accessing
exportHistogramFor: aDictionary By: aTypeString
	"TODO: quotes and retweets"
	| messagesByTimeSpan histogram diagram tempMessages |
	tempMessages := self perform: (aDictionary at: 'messagesType') asSymbol.
	tempMessages ifEmpty: [ self exportEmptyHistogramNamed: 
								(aDictionary at: 'messagesType'), '-histogram' ].
	aTypeString isNumber ifTrue: [ messagesByTimeSpan := tempMessages splitBytimeSpansOf: aTypeString ].
	(aTypeString = 'day' or: [ aTypeString = 'days' ])
		ifTrue: [ messagesByTimeSpan := tempMessages splitByDays ].
	(aTypeString = 'week' or: [ aTypeString = 'weeks' ])
		ifTrue: [ messagesByTimeSpan := tempMessages splitByWeeks ].

	histogram := RSChart new.
	histogram extent: (aDictionary at: 'extent').
	diagram := RSBarPlot new
		y: (messagesByTimeSpan values collect: [ :collection | collection size ]).
	"diagram color: (Color r:(91/255) g:(131/255) b:(222/255))."
	diagram color: (aDictionary at: 'color').
	histogram addPlot: diagram.
	histogram addDecoration: (RSHorizontalTick new
    	fromNames: messagesByTimeSpan keys;
    	labelRotation: 0;
		fontSize: 68 /messagesByTimeSpan size;
    	yourself).
    histogram addDecoration: (RSVerticalTick new 
		integer;
		fontSize: 68 /messagesByTimeSpan size).
	histogram build.
	^ histogram canvas exportAsFileNamed: (aDictionary at: 'messagesType'), '-histogram' into: self folder