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[birt-news] problems with stacked bar chart

I have the following data set, which lists the date, the period of time, and the number of users that were inactive within that period of time on that date.

 

01/01/2007 0 15

01/01/2007 7 10

01/01/2007 30 0

15/06/2007 0 21

15/06/2007 7 4

15/06/2007 30 5

 

I would like to build a stacked bar chart, which has one bar per distinct date (first column) and one stack per distinct period of time (second column). Each stack’s height will be set to the number of users (third column).

 

So, for the data set above I would have two bars: one – for 01/01/2007 and another one for 15/06/2007. The first bar will have three stacks on heights 15, 7 and 30. The second bar will also have three stacks with heights 21, 4 and 5.

 

I can map X-series to the first column, but I don’t know how to map each Y series to the corresponding period of time. In other words, I want one Y-series to be mapped to rows with interval=0, another series – to rows with interval = 7 and the last series – to rows with interval=30.

 

How should I define expressions for those series in _expression_ Builder?

 

Thanks.

 

Alec