A relative time reference in @if statements.
Time period detail is set in Defining, Deleting, and Displaying Time Periods.
True— if the period is in weekly detail
False—if not
If 2007 is in months and 2008 is in weeks, this formula:
@if(@isweek, 1, 2)
returns 2 in the months of 2007, and 1 in the weeks of 2008. Aggregate periods of 2008 returns 2.