You are very close. I believe you just need to change your calculation to:
SUM(Sales) > WINDOW_AVG(SUM(Sales))
What that will give you is a boolean result of true when the sum of Sales for a region is greater than the average of the sum of sales for all regions and false otherwise.
Hope that helps!
Thanks for your help Joshua! Using WINDOW_AVG is a pretty convenient calc to use.
Now if I was to add in Departments as a quick filter, is there any way I could show a reference line for the average sales in each department? And then whether or not that department is selected in my quick filter, the reference line would be hidden or visible?
I'm assuming instead of doing a pre-generated reference line, I'd have to create a calculated field That is something along the lines of
IF DEPARTMENT = 'Furniture' THEN WINDOW_AVG(SUM(SALES)) END
However, I get an error of "cannot mix aggregate and non aggregate values in an IF..."
Does this mean I need to use more calculated fields in some way?