Count the number of values in a list that match the current value

[Anonymous]

Hi everyone

I have a table CUSTOMER where there is a customer key that is a unique value and a list where that customer key is duplicated for each transaction the customer has done. I would like, in Power Query, to count the number of transactions per customer. Therefore I need to count the number of values in the list that are equal to the ID of the current row, for each row.

The reason I am not doing this in DAX is that I need this number to perform filtering on the table and eliminate some rows. 

How can I do it? Thanks 

[AlB]

Hi @Anonymous 

you can create a custom column with this code, where "IDColumn" is the name of the column with the IDs and "ListColumn" the name of the column with the lists:  

List.Count( List.Select ( [ListColumn],  (inner)=> inner = [IDColumn] ) )

Please mark the question solved when done and consider giving kudos if posts are helpful.

Contact me privately for support with any larger-scale BI needs

Cheers 

[Anonymous]

This looks correct and works rapidly when creating the column in PowerQuery but it's extremely slow when applying the query change. Is it normal or should it work smoothly?