accessing
exportTweetsHistogramWithBars: aNumberOfBars

	| tweetsByTimeSpan subtotals tweetsHistogram diagram |

	tweetsByTimeSpan := self collectMessages: [ self tweets] byTimeSpanSplits: aNumberOfBars.
	subtotals := tweetsByTimeSpan values collect: [ :collection | collection size ].
	tweetsHistogram := RSChart new.
	tweetsHistogram extent: 800@200.
	diagram := RSBarPlot new
		x: (1 to: subtotals size)
		y:subtotals.
	diagram color: (Color r:(91/255) g:(131/255) b:(222/255)).
	tweetsHistogram addPlot: diagram.
	tweetsHistogram addDecoration: (RSHorizontalTick new
    	fromNames: tweetsByTimeSpan keys;
    	labelRotation: 0;
		fontSize: 80 /aNumberOfBars;
    	yourself).
    tweetsHistogram addDecoration: (RSVerticalTick new 
		integer;
		fontSize: 80 /aNumberOfBars).
	tweetsHistogram build.
	tweetsHistogram canvas pngExporter 
		zoomToShapes;
		noFixedShapes; 
		fileName: (self folder / 'tweets-histogram.png')fullName;
		export.
	tweetsHistogram canvas pdfExporter 
		zoomToShapes;
		noFixedShapes; 
		fileName: (self folder / 'tweets-histogram.pdf')fullName;
		export.
	^ self folder / 'tweets-histogram.png'