I've two columns containing sales from last year and this year and a data column with the number of weeks we are in. I want to calculate a yearly rolling sum in a new column from the week we are in back in the past till that same week.
In my example if i'm in week 2 this year my rolling sum will be sum all the values of sales last year from week 2 til week 52 plus sales from this year until week 2 including!!
Here's an example in excel of what my table and results would look like: