accessing
tweetsByWeeksTimeSpan

	| weeks floor divisions tweetsByTimeSpan xAxis labels |
	weeks := ((self newestTweet created - self oldestTweet created) days / 7).
	floor := weeks floor.
	(weeks - floor) > 0.4 
		ifTrue: [ divisions := floor ] 
		ifFalse: [ divisions := floor + 1 ].
	tweetsByTimeSpan := self collectMessages: [ self tweets] byTimeSpanSplits: divisions.
	xAxis := OrderedCollection new.
	(tweetsByTimeSpan values collect: [ :collection | collection size ]) do: [ :number |
							xAxis add: ($' asString), (number asString), ($' asString)
																			].
	labels := OrderedCollection new.
	tweetsByTimeSpan keys do: [ :string |
	labels add: ($' asString), string, ($' asString)
							].
	^ {
	tweetsByTimeSpan.
	('[', (',' join: xAxis), ']').
	('[', (',' join: labels), ']').
	}