Aggregate Function to subtract previous Row value

JasonW

Be sure to look at John Wards article on Aggregate functions:<br />
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http://www.birt-exchange.org/devshare/designing-birt-reports/1102-working-with-extension-points-aggregations/#description<br />
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This funciton is a simple with very little error checking aggregate that supplies the diffference between two rows of data. For example

row number value  new Aggregate Value

1    30   0
2    33   3
3    25   -8

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An example report, the source and the deployable plugin are attached.