如何在Pandas中使用datetime index属性选择df的观测值？

Question

Given a df of this kind, where we have DateTime Index:

DateTime               A                           
2007-08-07 18:00:00    1
2007-08-08 00:00:00    2
2007-08-08 06:00:00    3
2007-08-08 12:00:00    4
2007-08-08 18:00:00    5
2007-11-02 18:00:00    6
2007-11-03 00:00:00    7
2007-11-03 06:00:00    8
2007-11-03 12:00:00    9
2007-11-03 18:00:00   10

I would like to subset observations using the attributes of the index, like:

• First business day of the month
• Last business day of the month
• First Friday of the month 'WOM-1FRI'
• Third Friday of the month 'WOM-3FRI'

I'm specifically interested to know if this can be done using something like:

df.loc[(df['A'] < 5) & (df.index == 'WOM-3FRI'), 'Signal'] = 1

Thanks

Answer 1

You could try...

# FIRST DAY OF MONTH
df.loc[df[1:][df.index.month[:-1]!=df.index.month[1:]].index]

# LAST DAY OF MONTH
df.loc[df[:-1][df.index.month[:-1]!=df.index.month[1:]].index]

# 1st Friday
fr1 = df.groupby(df.index.year*100+df.index.month).apply(lambda x: x[(x.index.week==1)*(x.index.weekday==4)])

# 3rd Friday
fr3 = df.groupby(df.index.year*100+df.index.month).apply(lambda x: x[(x.index.week==3)*(x.index.weekday==4)])

If you want to remove extra-levels in the index of fr1 and fr3 :

fr1.index=fr1.index.droplevel(0)
fr3.index=fr3.index.droplevel(0)