Identify new customers using date differences

Hi Anonymous ,

From your sample data and description I assume the following constraints:

• You only want to compare with the directly previous week, not with all previous weeks
• You have weekly data, every 7 days, so you only need to compare with exactly 7 days earlier, not with all dates in the previous week

Then try the following:

Count of new customers = 
VAR _selectedWeek = MAX ( 'Table'[Date] )
VAR _previousWeek = _selectedWeek - 7
VAR _customersSelectedWeek =
    CALCULATETABLE (
        VALUES ( 'Table'[Customer] ),
        'Table'[Date] = _selectedWeek
    )
VAR _customersPreviousWeek =
    CALCULATETABLE (
        VALUES ( 'Table'[Customer] ),
        'Table'[Date] =_previousWeek
    )
VAR _newCustomers = EXCEPT ( _customersSelectedWeek, _customersPreviousWeek )
VAR _countOfNewCustomers = COUNTAX ( _newCustomers, [Customer] )
RETURN
_countOfNewCustomers