SettingWithCopyWarning in pandas groupby mean()

Question

I have the following data frame. I wanted to create a new column from the output of pandas groupby().mean()

My code is:

df['AVG_CONSUMED_UNIT'] = df.groupby('transformer')['CONSUMED_UNIT'].transform('mean')

But I found this type of warning:

C:\Users\IGC\AppData\Local\Temp/ipykernel_9332/530264731.py:1: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

Any idea why this warning occured?

Input:

ID      CONSUMED_UNIT       transformer
1           100                 B/J-80
2           300                 B/J-80
3           150                 SHK-175
4           120                 ACV-17
5           80                  ACV-17

Output:

ID      CONSUMED_UNIT       transformer     AVG_CONSUMED_UNIT
1           100                 B/J-80          200
2           300                 B/J-80          200
3           150                 SHK-175         150
4           120                 ACV-17          100
5           80                  ACV-17          100

Waht is yoour code before `df['AVG_CONSUMED_UNIT'] = df.groupby('transformer')['CONSUMED_UNIT'].transform('mean')` ? There is some filtering? — jezrael, Feb 17 '22 at 11:44
@jezrael, yes, i used dropna() function to remove some missing values. — asif abdullah, Feb 17 '22 at 11:50
@asifabdullah - then use `df = df.dropna().copy()` for avoid warning — jezrael, Feb 17 '22 at 11:51
@jezrael, I forgot to reset the index. It's solved now. Thanks. — asif abdullah, Feb 17 '22 at 11:59

SettingWithCopyWarning in pandas groupby mean()

0 Answers0