I have rolling totals. I use above() function to get non rolling (just for that week) values. For e.g if week 1 has 5 count and week 2 has 10 (5+5 new) then I use the following expression to get just 5 for week 2. The logic fails when I have 0 for a week. e.g week 3. then in week 4 , I want to do week 4 count(cumulative) - week 2 count(cumulative) instead of week 4 count(cumulative) - week 3 count(cumulative). If several weeks in a row have 0 count I should be subtracting to last non zero count.
Sorry for being so confusing. Attaching the screenshot. A picture is worth a thousand words..
