Measure filtered by all available values for a field

[simonB2020]

I am looking to create a measure that is filtered only by the *available* values for a specific field.

So if I had classes 1,2 & 3  and a user filters on [country] & [product] , which as a byproduct only left classes 1 & 3 remaining,

Then I need to do a MAX on the entire data set for classes 1 & 3.

(there are lots more fields in the actual  app, and many more values for [class] !)

Current attempt was as below, but maybe I have misinterpreted the 'P' function ?

Max({1<[class_name]=P([class_name])>} [duration])

[rwunderlich · Accepted solution]

Your expression looks about right. Is it not returning the expected resul?

-Rob

[simonB2020]

Think this might be 'user error'
Sorry !