Calculating percentiles by group in Power BI - powerbi

Question

Below is a sample data and I am looking for a solution to calculate percentiles (25th, 50th, 75th, 100th) for quantity sold grouped by country.
So basically add countries into different buckets from low, mid 1, mid 2 or high depending upon the unit_quantity. So if I create a table shown below in power bi, I want to create a calculated measure that adds the countries into these different buckets.
Currently, what I have tried is create 3 different quartiles in below dax measure and then using IF function i have tried to put them in different buckets :
Quartile =
var FirstQ =
CALCULATE(
PERCENTILE.INC('Sample Table'[unit_quantity], .25),
ALLSELECTED('Sample Table')
)
var SecondQ =
CALCULATE(
PERCENTILE.INC('Sample Table'[unit_quantity], .5),
ALLSELECTED('Sample Table')
)
var ThirdQ =
CALCULATE(
PERCENTILE.INC(Sample Table'[unit_quantity], .75),
ALLSELECTED(Sample Table')
)
var currentVal = SELECTEDVALUE(Sample Table'[unit_quantity])
return
IF(currentVal <= FirstQ, "Low",
IF(currentVal > FirstQ && currentVal <= SecondQ, "Mid",
IF(currentVal > SecondQ && currentVal <= ThirdQ, "Mid 2", "High")
)
)
But the above measure calculates quartiles for the complete table and not grouped by country. Also I want this to be dynamic since I am going to have a slicer for category column so the percentile values should dynamically change according to the category. I am very new to power BI so please bear with me.

Answer 1

You can use PERCENTILEX to run a table calculation, in this case, all countries.
I've added a condition of ISFILTERED to only display the results if the country field is present.
Calculation
Quartile =
VAR SelectedUnit =
SUM ( 'Table'[unit_quantity] )
VAR p25 =
PERCENTILEX.INC (
ALLSELECTED ( 'Table'[country] ),
CALCULATE ( SUM ( 'Table'[unit_quantity] ) ),
0.25
)
VAR p50 =
PERCENTILEX.INC (
ALLSELECTED ( 'Table'[country] ),
CALCULATE ( SUM ( 'Table'[unit_quantity] ) ),
0.5
)
VAR p75 =
PERCENTILEX.INC (
ALLSELECTED ( 'Table'[country] ),
CALCULATE ( SUM ( 'Table'[unit_quantity] ) ),
0.75
)
RETURN
SWITCH (
ISFILTERED('Table'[country]),
SelectedUnit <= p25, "Low",
SelectedUnit > p25
&& SelectedUnit <= p50, "Mid",
"High"
)
Output
country
Unit Sum
Quartile
Bulgaria
2
Low
Canada
83
High
Croatia
49
Mid
India
75
High
Russia
38
Low
United States
69
High