Calculate average of last 52 mondays, tuesdays, etc...

[paolo_mapelli]

Good afternoon,

I've a dimension ("sales amount") related to a date dimension and I need to compare it with preceeding days having the same weekday.

For example, I've to compare sales amount for today, 20150825 (tuesday), with the average of (at most) last 52 tuesdays preceeding today.

Could you suggest a way to calculate this average ?

Thank you.

Paolo.