Computed items, are Fact columns that are created by the user and which use table data (or displayed Pivot data if Surface Values are enabled) as a basis for calculation. Each Pivot computed item is represented as a new Fact column in the Pivot display and Interactive Reporting provides a multitude of built-in data manipulation and evaluation functions for the user that facilitate the construction of computed item columns.
Here are some key points to remember when working with computed items in the Pivot section:
To ensure consistency, the source of data for computed items should be governed by the type of computed item function rather than being governed "globally" by the Surface Values property.
Computed Item functions that operate on aggregated data such as "Avg" and "ColMax" should always receive their input data from the underlying Results or Table data.
Computed Item functions that expect a single value as input, such as Sqrt, should receive their data from the displayed surface values.
Computed Items that refer directly to other Pivot section columns without wrapping in a Function reference (such as "Units Sold * 2" above, should receive this data always from displayed surface values.