pandas dataframe group year index by decade

Question

suppose I have a dataframe with index as monthy timestep, I know I can use dataframe.groupby(lambda x:x.year) to group monthly data into yearly and apply other oper

Answer 1

lets say your date column goes by the name Date, then you can group up

dataframe.set_index('Date').ix[:,0].resample('10AS', how='count')

Note: the ix - here chooses the first column in your dataframe

You get the various offsets: http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases