Problem calculated coloum vs measure

Hello,
It is incredible that PowerBI does not have a variable management such as qlik and tableau, I hope it will be implemented soon.
Yesterday I tried to study an alternative to get the matrix I need.
I feel that I am close to the solution but my knowledge does not help me.
I try to explain my reason:
I created a table with three columns, date column, shop column and parity column with two values a and c.
for each store I entered the values of the whole calendar with values c for every day that the store was closed while for all the remaining days.
here is the table.

and these are the relationships

creating the matrix object I have only one problem:
when I select a given silgola everything works correctly, when instead selecting a range of data the stores are displayed both in group a and in group c.
is there a way to display it in group c if there is no value a and in group a if there is a value a?