Pandas: Average value for the past n days

Question

I have a Pandas data frame like this:

test = pd.DataFrame({ \'Date\' : [\'2016-04-01\',\'2016-04-01\',\'2016-04-02\',
                                   


        

Answer 1

I think you can use first convert column Date to_datetime, then find missing Days by groupby with resample and last apply rolling

test['Date'] = pd.to_datetime(test['Date'])

df = test.groupby('User').apply(lambda x: x.set_index('Date').resample('1D').first())
print df
                 User  Value
User Date                   
John 2016-04-01  John    2.0
     2016-04-02  John    3.0
     2016-04-03   NaN    NaN
     2016-04-04   NaN    NaN
     2016-04-05   NaN    NaN
     2016-04-06  John    6.0
Mike 2016-04-01  Mike    1.0
     2016-04-02  Mike    1.0
     2016-04-03  Mike    4.5
     2016-04-04  Mike    1.0
     2016-04-05  Mike    2.0

df1 = df.groupby(level=0)['Value']
        .apply(lambda x: x.shift().rolling(min_periods=1,window=2).mean())
        .reset_index(name='Value_Average_Past_2_days')

print df1
    User       Date  Value_Average_Past_2_days
0   John 2016-04-01                        NaN
1   John 2016-04-02                       2.00
2   John 2016-04-03                       2.50
3   John 2016-04-04                       3.00
4   John 2016-04-05                        NaN
5   John 2016-04-06                        NaN
6   Mike 2016-04-01                        NaN
7   Mike 2016-04-02                       1.00
8   Mike 2016-04-03                       1.00
9   Mike 2016-04-04                       2.75
10  Mike 2016-04-05                       2.75
11  Mike 2016-04-06                       1.50

print pd.merge(test, df1, on=['Date', 'User'], how='left')
        Date  User  Value  Value_Average_Past_2_days
0 2016-04-01  Mike    1.0                        NaN
1 2016-04-01  John    2.0                        NaN
2 2016-04-02  Mike    1.0                       1.00
3 2016-04-02  John    3.0                       2.00
4 2016-04-03  Mike    4.5                       1.00
5 2016-04-04  Mike    1.0                       2.75
6 2016-04-05  Mike    2.0                       2.75
7 2016-04-06  Mike    3.0                       1.50
8 2016-04-06  John    6.0                        NaN