How can I further optimize this DAX formula?

Hi markus_zhang

 Unless I'm missing something, what your code does in a slightly convoluted manner is count how many users (emails) have logged in on the date selected in the slicer or any of the previous [ActiveThreshold] days. If so, you can simplify the code a whole lot:

Measure =
IF (
    ISFILTERED ( WeekMatrix[Date] ),
    VAR _SelectedDate = SELECTEDVALUE ( WeekMatrix[Date] )
    RETURN
        CALCULATE (
            DISTINCTCOUNT ( NTKLogin[email] ),
            NTKLogin[logins] <= _SelectedDate, NTKLogin[logins] >= _SelectedDate - [ActiveThreshold]
        ),
    ERROR ( "This measure can only be evaluated under the filter context of WeekMatrix[Date]" )
)