st: PLEASE, Cumulative by group

["Mohamad Al-Ississ" <Mohamad_Al-Ississ@ksg07.harvard.edu>]

Hi,
I am wondering if you can help me. I am trying to get a cumulative sum
of AAR below by dif group. So I need the CAAR to do something like
this:

dif   AAR       CAAR
1     2.2         2.2
1     2.2         2.2
1     2.2         2.2
1     2.2         2.2
2     6.6         8.8
2      6.6        8.8
2      6.6        8.8
2      6.6        8.8
3      1.4        10.2
3      1.4        10.2
3      1.4        10.2

I cannot do by line because because the groups vary in number of
sub_occupants. I need to do it by group, can you help me?
Thanks,
--
Mohamad Al-Ississ
Candidate, Masters in Public Administration
in International Development,
Kennedy School of Government
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