Pandas Rolling On A Shifted Dataframe

Here's a piece of code, I don't get why on the last column rm-5, I get NaN for the first 4 items. I understand that for the rm columns the 1st 4 items aren't filled because there i

Solution 1:

You can change the order of operations. Now you are first shifting and afterwards taking the mean. Due to your first shift you create your NaN's at the end.

index = pd.date_range('2000-1-1', periods=100, freq='D')
df = pd.DataFrame(data=np.random.randn(100), index=index, columns=['A'])

df['rm']=pd.rolling_mean(df['A'],5)
df['shift'] = df['A'].shift(-5)
df['rm-5-shift_first']=pd.rolling_mean(df['A'].shift(-5),5)
df['rm-5-mean_first']=pd.rolling_mean(df['A'],5).shift(-5)

print( df.head(n=8))
print( df.tail(n=8))

                   A        rmshift  rm-5-shift_first  rm-5-mean_first
2000-01-01 -0.120808       NaN  0.830231               NaN         0.184197
2000-01-02  0.029547       NaN  0.047451               NaN         0.187778
2000-01-03  0.002652       NaN  1.040963               NaN         0.395440
2000-01-04 -1.078656       NaN -1.118723               NaN         0.387426
2000-01-05  1.137210 -0.006011  0.469557          0.253896         0.253896
2000-01-06  0.830231  0.184197 -0.390506          0.009748         0.009748
2000-01-07  0.047451  0.187778 -1.624492         -0.324640        -0.324640
2000-01-08  1.040963  0.395440 -1.259306         -0.784694        -0.784694
                   A        rmshift  rm-5-shift_first  rm-5-mean_first
2000-04-02 -1.283123 -0.270381  0.226257          0.760370         0.760370
2000-04-03  1.369342  0.288072  2.367048          0.959912         0.959912
2000-04-04  0.003363  0.299997  1.143513          1.187941         1.187941
2000-04-05  0.694026  0.400442       NaN               NaN              NaN
2000-04-06  1.508863  0.458494       NaN               NaN              NaN
2000-04-07  0.226257  0.760370       NaN               NaN              NaN
2000-04-08  2.367048  0.959912       NaN               NaN              NaN
2000-04-09  1.143513  1.187941       NaN               NaN              NaN

For more see:

http://pandas.pydata.org/pandas-docs/stable/computation.html#moving-rolling-statistics-moments

http://pandas.pydata.org/pandas-docs/dev/generated/pandas.DataFrame.shift.html