Set Analysis - how to select a prior period exchange rate

[paul_ripley]

Hello

I have a report whereby I want to pick up in a column, the previous month FX rate.

Ie if I select this period I want to show the last months exchange rate

I've tried various things that don't quite work

The below works for the latest set of exchange rates loaded into the system

I would like the latest - 1 period

only({$<[Exchange Rates Period] = {"$(=max(period))"}>}     [Exchange Rates Cur to GBP])

so I thought this would work

only({$<[Exchange Rates Period] = {"$(=max(period)-1)"}>}     [Exchange Rates Cur to GBP])

Can anyone see what I am doing wrong?

Many thanks

Paul

[Gysbert_Wassenaar · Accepted solution]

The expression won't work if period is not a number or you're using Exchange Rates Period as chart dimension and expect each Exchange Rates Period row to display a value from another period. The set is calculated at the chart level, not the row level.

Perhaps this document helps: Calculating rolling n-period totals, averages or other aggregations

[paul_ripley]

thanks