Calculate average orders customer first, second, third etc. month

Hi Anonymous 

Try this:

1. Create a 1-to-many unidirectional relationship between UserTable[UserID] and OrdersTable[UserID]

2. Create a one-column calculated table:

AuxTable = 
VAR _MaxDiff =
    MAXX (
        ADDCOLUMNS (
            UserTable;
            "MonthDiff"; DATEDIFF (
                UserTable[Creation User Date];
                CALCULATE ( MAX ( OrdersTable[Order Date] ) );
                MONTH
            )
        );
        [MonthDiff]
    )
RETURN
    SELECTCOLUMNS ( GENERATESERIES ( 1; _MaxDiff + 1); "MonthSinceCreation"; [Value] )

3. Place AuxTable[MonthSinceCreation] just created in the previous step in the rows of a matrix visual

4. Create this measure and place it in values of the matrix visual:

AverageAmountOrders = 
AVERAGEX (
    ALL ( UserTable);
    CALCULATE (
        COUNT ( OrdersTable[Order Date] );
        FILTER (
            CALCULATETABLE ( OrdersTable );
            DATEDIFF ( UserTable[Creation User Date]; OrdersTable[Order Date]; MONTH )
                <= (SELECTEDVALUE ( AuxTable[MonthSinceCreation] ) - 1)
        )
    )
) + 0