DAX: How to count customers who buys the month of april only and not the others.

[Charles59]

Hi everyone, 

I have an issue on DAX that I can't solve, maybe someone could help. 

Here is my example

My problem: I would like to count the number of new customers who bought in April ONLY and not during previous months. 

In our case, 2 new customers (customer C & D)

Let's imagine a purchase teble like below: 

Customer	Month of purchase
A	1
A	2
A	4
B	1
B	3
C	4
C	4
D	4

[ThxAlot · Accepted solution]

Apr ONLY = 
CONCATENATEX(
    FILTER(
        CALCULATETABLE( VALUES( SALES[Customer] ), SALES[Month of purchase] = 4 ),
        CALCULATE( ISEMPTY( SALES ), SALES[Month of purchase] <> 4 )
    ),
    SALES[Customer],
    ", "
)

[HassanAshas]

Please try the following, 

Count of People = 

var _OtherCustomers = 
    CALCULATETABLE(
        VALUES('Table'[Customer]), 
        'Table'[Month of purchase] < 4
    )

var _Result =
    COUNTROWS(
        SUMMARIZE(
            FILTER(
                'Table', 
                'Table'[Month of purchase] = 4
                &&
                NOT('Table'[Customer] in _OtherCustomers)
            ), 
            'Table'[Customer]
        )
    )

return _Result

The idea is to, 

• Find out the Customers who have purchases in the Months less than "4"
• Filter the Table to only find the people who have done purchases in the Month = 4 and also filter out those Customers in this table who belong to the first list (_OtherCustomers as caluclated above)
• Summarize this resultant table based upon Customer (so as to find unique number of Customers)
• Finally count the Rows in the summarized table. This should give you your final answer.