RANKX does not give the correct result - powerbi

Question

I need to create a measure (not column) that would rank users based on value.
Here I am trying to use RANKX function:
ranking =
RANKX(
ADDCOLUMNS(
SUMMARIZE(dim_User,
dim_User[UserID],
dim_User[FirstName]
),
"Ttl Trans", [Ttl Transactions]
)
, [Ttl Transactions]
)
Same result using:
rating2 =
RANKX(
SUMMARIZE(dim_User,
dim_User[FirstName]
), [Ttl Transactions]
)
Tried this way:
rating1 =
RANKX(
SUMMARIZE(dim_User,
dim_User[FirstName],
"Trans",[Ttl Transactions]
), [Trans]
)
But gives me an error:
The value for 'Trans' cannot be determined. Either the column doesn't exist, or there is no current row for this column.
I also tried using COUNTROWS() function, but also no success.
It seems like it works if I use a table, not a table expression.
What am I missing here?
UPDATE:
Adding ALL(dim_User) still giving me 1
ranking =
RANKX(
ADDCOLUMNS(
SUMMARIZE(ALL(dim_User),
dim_User[UserID],
dim_User[FirstName]
),
"Ttl Trans", [Ttl Transactions]
)
, [Ttl Transactions]
)
UPDATE
No matter what user I select, in a rating in a card is always 1.

Answer 1

When you write a measure, it is evaluated within its local filter context. In particular, dim_User is filtered by FirstName within your measure and is, therefore, ranking Ttl Trans only compared to other users with the same FirstName.
Since you are ranking based on user, you want to remove the filter context introduced by the visual in order to get the ranking you expect. I'd suggest replacing the table argument dim_User with ALL(dim_User) to remove all filtering on that table or -- more likely the option you want -- with ALLSELECTED(dim_User) to remove the local filter context introduced by the visual while maintaining any filter context from slicers or page-level filters.
For your card, you'll need to simulate the filter context that exists in the table:
UserRanking =
VAR SelectedUser = SELECTEDVALUE ( dim_User[Name_FirstLast] )
RETURN
CALCULATE (
RANKX ( ALL ( dim_User ), [Ttl Transactions] ),
dim_User[Name_FirstLast] = SelectedUser
)