Replace Nan values with the minimum value in the same parent class

user_17908075 0
Viewed 65
country      count

Argentina     3
Argentina     4
Argentina    NaN
Wales         1
Wales         3
Wales        NaN

Nan values, I want to make a minimum of the values that share the same countries as the NaN value.

Output Should Be:

Argentina     3
Argentina     4
Argentina     3
Wales         1
Wales         3
Wales         1

I tried bfill method but didn't manage this. Thank You For Help

pandas
1 Answers

One way is using map, groupby and fillna

map allows you to match by an index, when you create a groupby object it defaults to creating an index, (as_index=True) so it's pretty simple to map it back to your main dataframe.

df['count']  = df['count'].fillna(
          df['country'].map(df.groupby('country')['count'].min()))



print(df)

     country  count
0  Argentina    3.0
1  Argentina    4.0
2  Argentina    3.0
3      Wales    1.0
4      Wales    3.0
5      Wales    1.0

a simplier method is to use .transform which applies groupby operations without modifying the index

df['count'] = df['count'].fillna(
               df.groupby('country')['count'].transform('min'))

     country  count
0  Argentina    3.0
1  Argentina    4.0
2  Argentina    3.0
3      Wales    1.0
4      Wales    3.0
5      Wales    1.0
user_93751020
Related