Calculate number of distinct dates in a table with conditions in other columns

[prattja9]

Greetings, 

I have a table of data about tests. Individual ID's can take more than one test in a given day. I'm trying to compute a column that calculates the number of distinct dates in the table per ID. So for example:

ID	Subject	Date
1	Math	1/1/2022
2	Science	2/2/2022
2	Math	2/2/2022
3	English	3/1/2022
3	Math	3/1/2022
3	Math	4/1/2022

With my expect result being: 

ID	Subject	Date		Unique Dates by ID
1	Math	1/1/2022		1
2	Science	2/2/2022		1
2	Math	2/2/2022		1
3	English	3/1/2022		2
3	Math	3/1/2022		2
3	Math	4/1/2022		2

I've tried various combinations using calculate, summarize, and sumx. And I can get the value I expect in a visual by using distinct count, but I can't get it to work with DAX. 

Thanks!

[rsbin · Accepted solution]

@prattja9 ,

Your Calculated Column is:

UniqueDatesbyID = CALCULATE( DISTINCTCOUNT( [Date] ),
                             ALLEXCEPT( Tests, Tests[ID] ))

Trust this is what you are looking for.

Regards,