In [25]:
cohorts.set_index(['FirstOrder','CohortPeriod'],inplace=True)
cohorts.head()
Out[25]:
OrderPeriod TotalUsers
FirstOrder CohortPeriod
2009-01 0 2009-01 22.0
1 2009-02 8.0
2 2009-03 10.0
3 2009-04 9.0
4 2009-05 10.0