In [11]:
df['FirstOrder']=FirstOrder
df.reset_index(inplace=True)
df.head()
Out[11]:
UserId OrderId OrderDate OrderPeriod FirstOrder
0 47 262 2009-01-11 2009-01 2009-01
1 47 278 2009-01-20 2009-01 2009-01
2 47 294 2009-02-03 2009-02 2009-01
3 47 301 2009-02-06 2009-02 2009-01
4 47 302 2009-02-06 2009-02 2009-01