Pandas how to find Quartile of dataframe per each key in a row-CodePudding

What i need to find is for all my keys values what is the 3rd quartile? then I would need to display that information in some way for each Key. below is an example of what im looking for but the 2nd dataframe can look different

Dataframe A   -> Dataframe A
Key, value       key, value, Quartile(3rd)
A    2           A    2      result of third quartile here X as placeholder
B    3           B    3      result of third quartile here Y as placeholder
A    4           A    4      x
A    5           A    5      x
A    6           A    6      x
B    6           B    6      y
C    1           C    6      z
etc

The quartile doesn't need to be inserted into a new column i just need to know for all my A values what is the 3rd Quartile.

CodePudding user response：

You can use GroupBy.quantile with 0.75 for the 75% quantile (3rd quartile):

df.groupby('Key')['value'].quantile(0.75)

output:

Key
A    5.25
B    5.25
C    1.00
Name: value, dtype: float64

To repeat the values for all rows per group you can use transform:

df['Quartile(3rd)'] = df.groupby('Key')['value'].transform(lambda s: s.quantile(0.75))

output:

  Key  value  Quartile(3rd)
0   A      2           5.25
1   B      3           5.25
2   A      4           5.25
3   A      5           5.25
4   A      6           5.25
5   B      6           5.25
6   C      1           1.00