In [15]:
cohorts.rename({'UserId':'TotalUsers'},axis=1,inplace=True)
cohorts.head()
Out[15]:
FirstOrder OrderPeriod TotalUsers
0 2009-01 2009-01 22
1 2009-01 2009-02 8
2 2009-01 2009-03 10
3 2009-01 2009-04 9
4 2009-01 2009-05 10