|Member_Expression||MDX expression that returns a member.|
PreviousPeriods returns optimized set of previous periods that can be used to aggregate some measure value for all previous time periods. The function often used for cumulative values over time, for example, default measure Cumulative story points resolved, or when all activities of previous periods should be considered to get value for a current period, for example, default measure Open issues - all previously created and resolved issues; default measure Issues history - all previous changes in the issue to see the current state or the state at the end of any period.
Here is in more depth how it works. For example,
PreviousPeriods( [Time]..[Q2 2015].[Jun 2015].[Jun 03 2015] ) will return a set:
which is all years until previous year (in this example Time dimension starts with year
2014), all current year quarters until previous quarter (in this example
Q1 2015), all current quarter months until the previous month (
Apr 2015 and
May 2015) and all current month days until the previous day (
Jun 01 2015 and
Jun 02 2015).
The following formula can be used to calculate a cumulative sum of resolved issues until the previous period:
If we want to calculate a cumulative sum of resolved issues including the current period then we need to add the current period to the previous periods set: