Shows the calculation of lost customers based upon sales fact using DAX for SSAS Tabular

DAXLostCustomers.txt

Lost Customers :=
 IF (
     NOT (
         MIN ( 'Date'[Full Date] )
             > CALCULATE ( MAX ( Sales[Invoice Date] ), ALL ( Sales ) )
     ),
     COUNTROWS (
         FILTER (
             ADDCOLUMNS (
                 FILTER (
                     CALCULATETABLE (
                         ADDCOLUMNS (
                              CALCULATETABLE ( 
                                 VALUES ( Customer[Customer No] ), Sales ),
                                 "CustomerLostDate", CALCULATE (
                                     MAX ( Sales[Invoice Date] ),
                                     ALLEXCEPT ( Customer, Customer[Customer No] )
                              )
                                  + [Lost Days Limit]
                          ),
                         FILTER (
                             ALL ( 'Date' ),
                             AND (
                                 'Date'[Full Date] < MIN ( 'Date'[Full Date] ),
                                 'Date'[Full Date] >= 
                                     MIN ( 'Date'[Full Date] ) - [Lost Days Limit]
                             )
                         )
                     ),
                     AND (
                         AND (
                             [CustomerLostDate] >= MIN ( 'Date'[Full Date] ),
                             [CustomerLostDate] <= MAX ( 'Date'[Full Date] )
                         ),
                         [CustomerLostDate] <=  
                            CALCULATE ( MAX ( Sales[Invoice Date] ), ALL ( Sales )                            )
                     )
                 ),
                 "FirstBuyInPeriod", CALCULATE ( MIN ( Sales[Invoice Date] ) )
             ),
             OR ( 
                ISBLANK ( [FirstBuyInPeriod] ), 
                [FirstBuyInPeriod] > [CustomerLostDate] 
             )
         )
     )
 )