Hi,
I want to make a chart with the sum of "quantity" for the current period and for 11 previous periods. I.e. 12 months/periods.
I'm using the following expression in a chart:
=
sum({$<created_per={$(=Max(created_per))}>}quantity)
created_per is the period in format YYYYMM. This expression works fine, and shows the latest period in my chart.
However, if i write expressions like this for each record:
= sum({$<created_per={$(=Max(created_per)-1)}>}quantity)
= sum({$<created_per={$(=Max(created_per)-2)}>}quantity)
= sum({$<created_per={$(=Max(created_per)-3)}>}quantity)
It does not work, because when subtracting 1 from the period 201101, it becomes 201100 - which obviously is not a valid period. Instead of 201100 I would of course need to get 201012.
Any suggestions for how to solve this? How do I refer to the previous record in the created_per "column".
