What I would like to calculate is the additional online sales in case the shop would sell the same % online per product as all shops together. I was able to generate a summarized table that calculates the "additional online sales"
But as the original data has more then 1 million rows and I need to apply quite a lot of filters I could like to include the calculation of additional online sales in a measure so that all the report filters get applied (filters based on linked tables). I tried to include the code above in a measure
GOOD PIECE OF ADVICE: Do not use SUMMARIZE for obtaining figures. Use this function ONLY for getting the combinations of values against which you want to calculate numbers. Instead, use the combination of SUMMARIZE/ADDCOLUMNS.
SUMMARIZE is a very complex function that has many bugs into the bargain. Complex in this context means it's very often doing something different from what you think it should.
If you want to know why you shouldn't do that please refer to the articles on SUMMARIZE at www.sqlbi.com.