如何从 Pandas dataframe 中的分钟数据中删除每日平均值

Question

I have a pandas dataframe with a minute datetime index:

Index	Col1
2022-12-25 09:01:00	5
2022-12-25 09:10:00	15
2022-12-25 11:12:00	10
2022-12-26 10:05:00	2
2022-12-26 12:29:00	2
2022-12-26 13:56:00	5

I want to remove the daily average from this data, resulting in this dataframe (here 10 for the first day and 3 for the second day):

Index	Col1
2022-12-25 09:01:00	-5
2022-12-25 09:10:00	5
2022-12-25 11:12:00	0
2022-12-26 10:05:00	-1
2022-12-26 12:29:00	-1
2022-12-26 13:56:00	2

Answer 1

Assuming df is your dataframe, this should do the trick:

for day, df_group in df.groupby(by=df.index.day):
    
    df.loc[df_group.index,"Col1"] -= df_group["Col1"].mean()