Filtering aggregate values
You can use filters to display aggregate values according to certain conditions. Because BIRT Studio displays only a preview of up to 200 rows of the actual data, when you perform actions such as aggregating data, or filtering aggregate data values, the resulting report design displays different results in BIRT Studio and in Actuate BIRT Viewer. This disparity occurs because BIRT Studio applies the specified aggregation function to the previewed data, and applies the filter condition to this subset of data.
When you view a report created in BIRT Studio, in the BIRT viewers, all data rows are retrieved and displayed in the report design. If you now create an aggregate calculation in Interactive Viewer, the aggregate function is applied across all rows of data in the report design. If you create a filter condition for the aggregate data, the filter is also applied across all rows of data, resulting in more accurate results. Always view the report design in Actuate BIRT Viewer to verify that the results are what you expect.
When you create a filter condition that excludes certain values, such as viewing transactions that closed over a month ago or listing products that are not the top five selling products, BIRT Studio recalculates the aggregate data according to the data BIRT Studio retrieves. In some cases, it is also useful to view aggregate values for the unfiltered data, for example, to perform percentage calculations on this data.
To address both situations in detail tables containing aggregate data, BIRT Studio provides an option on the Filter, Advanced Filter, and Top/Bottom N filter dialog boxes that enables a user to specify whether to recalculate aggregate data based on the filter condition created, or not.
To create a filter on aggregate values, complete the following steps:
In BIRT Studio, select the aggregate value, then choose FilterFilter, or FilterFilter Top/Bottom N from the context menu, as shown in Figure 4-26.
Figure 4-26  
BIRT Studio executes the filter condition, and displays the resulting data in the report design.
Run the report in Actuate BIRT Viewer to verify that the results are what you expect.

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