BUG: Timegrouping not mirroring resample when groupby is a list indexer #10084
Description
so it appears that [9] is wrong, should be consistent with [7],[8]
In [1]: index = date_range('20130101',freq='2D',periods=6) In [2]: df = DataFrame(np.arange(20).reshape(5,4),columns=list('ABCD'),index=index.take([0,1,2,3,4])) In [3]: df.resample('2D',how='max') Out[3]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-07 12 13 14 15 2013-01-09 16 17 18 19 In [4]: df.groupby(pd.Grouper(level=0,freq='2D')).max() Out[4]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-07 12 13 14 15 2013-01-09 16 17 18 19 In [5]: df.groupby([pd.Grouper(level=0,freq='2D')]).max() Out[5]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-07 12 13 14 15 2013-01-09 16 17 18 19 In [6]: In [6]: df = DataFrame(np.arange(20).reshape(5,4),columns=list('ABCD'),index=index.take([0,1,2,4,5])) In [7]: df.resample('2D') Out[7]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-07 NaN NaN NaN NaN 2013-01-09 12 13 14 15 2013-01-11 16 17 18 19 In [8]: df.groupby(pd.Grouper(level=0,freq='2D')).max() Out[8]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-07 NaN NaN NaN NaN 2013-01-09 12 13 14 15 2013-01-11 16 17 18 19 In [9]: df.groupby([pd.Grouper(level=0,freq='2D')]).max() Out[9]: A B C D 2013-01-01 0 1 2 3 2013-01-03 4 5 6 7 2013-01-05 8 9 10 11 2013-01-09 12 13 14 15 2013-01-11 16 17 18 19