What I tried so far was to create a calculated value:
SUM([Net Sales EUR])-(WINDOW_AVG(SUM([Net Sales EUR]),FIRST(),LAST()))
And put this on the color mark. However I am unsure if this actually works. Have not found a way to calculate the season adjusted row averages.
Thanks Michel. I was trying to do almost the same thing and your expression above was helpful. I am graphing monthly sales over a 1 year period, as well as the seasonal index which I've expressed as follows:
sum([Sales])/sum(Window_Avg(Sum([Sales]), First(), Last())
Question for you - do you think there is a way to calculate this on a calendar year basis, regardless of how many years are displayed on the graph? In other words, if I am graphing 2010 through 2013 monthly data, I would like each month's sales in 2010 to be divided by the average monthly 2010 sales, and likewise for 2011, 2012, 2013 (different denominators depending on the calendar year). Any help would be greatly appreciated.