Distintcount on PersonID if true in another column

[MickeLearnPBI]

I want to count distinctcount on personid that has true in another column.
Really scratching my head right now. Anyone can give me some support in this?

PersonID	Active
4505010101	True
4709010101

[some_bih]

Hi @MickeLearnPBI possible solution, based on simple data sample from you and my add of two rows:

Firstly, create measure as following (replace your table name for Mytable)

CountRows = COUNTROWS(Mytable)

Second, create calculated column like below Active_as_mesure

Active_as_mesure =

IF([CountRows]=1,"True","")

Output 

[MickeLearnPBI]

Maybe the report can help to understand me?

Shared with you - OneDrive (live.com)

[MickeLearnPBI]

I still get the number 8 in my data, that is 6 with the value null, and 2 with true. But with this the number change while choosing another year (above is not my fully report). Do you have any idea?