Count the Variable when it appear the first time

[Yqy]

Hi, i have a table with many variables and it have duplicates, what i want to do is to have count for the variable when it appear the first time and does not count the variable when is appear the second time onwards.

Var		Var	Count
A		A	1
A		A	null
B		B	1
B		B	null
C		C	1
D		D	1

[Ritaf1983]

Hi @Yqy 
You can achieve it with 2steps :
1 . In PQ add the index column:

2. In the Data editor add a column with this Dax:

first occurrence check =

IF (

    CALCULATE (

        COUNTROWS ( 'Table' ),

        FILTER (

            ALLEXCEPT ( 'Table','Table'[Var]),

            'Table'[Index] <= EARLIER (  'Table'[Index] )

        )

    )

        > 1,

    blank(),

    1

)

Link to a sample file 

If this post helps, then please consider Accepting it as the solution to help the other members find it more quickly.

[Yqy]

Hi, is it possible to do the second step in Query using M language instead of in the data editor using DAX

[Ritaf1983 · Accepted solution]

Hi again, 
Yes, it is possible please follow these few steps (after adding index column):
1. Group by with counting all rows:

2. Expand only index

3. Add a conditional column

4. remove unnecessary columns
RESULT :

Link to a updated sample file 

If this post helps, then please consider Accepting it as the solution to help the other members find it more quickly.

[Yqy]

Thanks for the help, your solution works.

[Ritaf1983]

I was happy to help 😊