Tableau Summing up aggregated data with FIXED

Question

Data is broken down by client, invoice date, and product category.

The volume each week is calculated using a moving average. MA Volume depending on the last 12 weeks: window sum(sum([Volume]),-11,0)/window count(count([Volume]), -11,0)/window sum(sum([Volume]),-11,0)

We need to look at the current week's deviation vs. the MA for that week (Vol DIFF): [MA Calc] SUM([Volume])

We need to add up the variances for a specific time period (year/month). Essentially, this should inform us if we depart positively or adversely from the baseline on average over a particular length of time.
Unfortunately, I receive errors such as:

"The argument to SUM (an aggregate function) is already an aggregation and cannot be aggregated further." "Table computations or the ATTR function cannot be used in level of detail expressions," for example.

Do you have any suggestions on how I may improve my situation?

Answer 1

I was able to solve this puzzle. It was necessary to add months to the view before using WINDOW SUM(Vol DIFF). It's that simple!