Trouble averaging specific rows in Pandas DataFrame

问题

I currently have the following two DataFrames:

raw_data=

     Time                             F1         F2        F3
2082-05-03 00:00:59.961599999  -83.769997      29.430000      29.400000   
2082-05-03 00:02:00.009600000  -84.209999      28.940001      28.870001   
2082-05-03 00:02:59.971200000  -84.339996      28.280001      28.320000

outage_by_timeofday_num = (made from raw_data) (ignore dashes - they are for alignment only)

                              F1     F2    F3  
Time                                                                        
2082-05-03 00:00:00           0      1     1   
2082-05-03 01:00:00           0      1     1

I've been able to sort and average the raw_data DataFrame by times of the day using the following code (below), but I'm unable to do the same with the outage_by_timeofday_num DataFrame:

This works:

raw_data = pd.read_excel(r'/Users/linnk ....
raw_data[u'Time']= pd.to_datetime(raw_data['Time'], unit='d')    
raw_data.set_index(pd.DatetimeIndex(raw_data[u'Time']), inplace=True) 
raw_data.Time = pd.to_datetime(raw_data.Time)

def time_cat(t):
    hour = t.hour
    if(hour >= 5 and hour < 9):
        return 'Morning (5AM-9AM)'
    elif(hour >= 9 and hour < 18):
        return 'Day (9AM-6PM)'
    elif(hour >= 18 and hour < 22):
        return 'Evening (6PM-10PM)'
    else:
        return 'Night (10PM-5AM)'

by_timeofday = raw_data.groupby(raw_data.Time.apply(time_cat)).mean()

and the by_timeofday output is:

                        F1              F2             F3  
Time                                                                       
Day (9AM-6PM)         -47.301852      23.070963      22.981000   
Evening (6PM-10PM)    -50.033000      24.011667      23.921833   
Morning (5AM-9AM)     -62.481130      48.417866      48.537197   
Night (10PM-5AM)      -71.372613     -71.289763      53.957411 \

This, however, does not work:

outage_by_hour_num.Time= pd.to_datetime(outage_by_hour_num.Time)
outage_by_timeofday = outage_by_hour_num.groupby(outage_by_hour_num.Time.apply(time_cat)).sum(axis=1, numeric_only=True)

This gives the error: AttributeError: 'DataFrame' object has no attribute 'Time'

Can someone help me spot my error/the edit I need to make to sort my outage_by_timeofday_num DataFrame in the same way I sorted raw_data? In case it might be useful, outage_by_timeofday_num has been made in the following way:

ave_data = raw_data.resample('h', how='mean')
ave_data.index.name=u'Time'
summary_ave_data = ave_data.copy()
summary_ave_data['Hourly Substation Average'] = summary_ave_data.mean(numeric_only=True, axis=1)
outage_by_hour = summary_ave_data >= 0.05
outage_by_hour_num= outage_by_hour.astype(int)

回答1:

You got rid of your 'Time' column in ave_data.index.name=u'Time'. Change it with:

ave_data.set_index('Time', drop=False, inplace=True)

That makes sure you set it as an index, but you keep the 'Time' column.

来源：https://stackoverflow.com/questions/31783944/trouble-averaging-specific-rows-in-pandas-dataframe

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python

datetime

pandas

dataframe

average