Using GROUPBY with PERCENTILEX as expression

[Majfah]

Hi guys, 

I have dataset containing three columns
- Department

- Timestamp

- NbrOfCustomers
From this table I would like to compute another table containtng the 90-th percentiles of NbrOfCustomers for each Department. It has to be a proper table as I am to use it in further calcualtions. I have tried the following DAX formula
 

GROUPBY(MyDataset; MyDataset[Department]; "90th Percentile"; PERCENTILEX.INC(CURRENTGROUP(); MyDataset[NbrOfCustomers]; 0,9))

which works like a charm when using SUMX, AVERAGEX etc as expression. But for some reason it does not work with the PERCENTILEX. I get the following error message

"Function 'GROUPBY' scalar expressions have to be Aggregation functions over CurrentGroup(). The expression of each Aggregation has to be either a constant or directly reference the columns in CurrentGroup()."

Why is this? 

[v-yulgu-msft]

Hi @Majfah,

From this document, we can see that:

"The CURRENTGROUP function takes no arguments and is only supported as the first argument to one of the following aggregation functions: AverageX, CountAX, CountX, GeoMeanX, MaxX, MinX, ProductX, StDevX.S, StDevX.P, SumX, VarX.S, VarX.P." PERCENTILEX is not a supported function to be used inside CURRENTGROUP() function.

Regards,

Yuliana Gu