difference from previous Friday

Hi,

I am not sure how your datamodel looks like, but I tried to create a sample pbix file like below.

There are some ways to achieve this, and I think it depends on how the business process for Saturday and Sunday is defined. I assume there are blank (not zero) data on Sat and Sun, and one of ways to achieve this is using lastnonblank DAX function.

Diff %: =
VAR _currentdate =
    MAX ( 'Calendar'[Date] )
VAR _lastnonblank =
    CALCULATE (
        LASTNONBLANK ( 'Calendar'[Date], [Value sum:] ),
        FILTER ( ALL ( 'Calendar'[Date] ), 'Calendar'[Date] < _currentdate )
    )
VAR _lastnonblankvalue =
    CALCULATE ( [Value sum:], 'Calendar'[Date] = _lastnonblank )
RETURN
    IF (
        NOT ISBLANK ( [Value sum:] ) && HASONEVALUE ( 'Calendar'[Date] ),
        DIVIDE ( [Value sum:] - _lastnonblankvalue, _lastnonblankvalue )
    )