Create a column referencing indirect relationship between tables

[chat_peters]

Hello,

I need to create a calculated column in the Cat table (data model below) for filtering purposes. I want to see the total count of Period ID  for each Cat ID. Both fields are highlighted in yellow. I do not want to use USERELATIONSHIP.  PBIX File Link 

Thank you for taking the time to read!

[lbendlin · Accepted solution]

Column = CALCULATE(DISTINCTCOUNT(Period[Period ID]),TREATAS({[Group ID]},Period[Group ID]))

What made you use the bidirectional relationship? I would change the data model to