st: loop question

[Sandu Cojocaru <scojocaru@gmail.com>]

Dear All:

I'm having trouble generating a variable that for each member i equals
sum(Cj-Ci) over all Cj>Ci where i and j are members of the same group.
Here's an example of the data setup - I'm trying to calculate
`outcome_var'.
For row 1 outcome_var=0, for row 3 = (200-100)+(300-100) = 300...and so on...

group_id       member_id       C           outcome_var
1                  1                     300        0
1                  2                     200        100
1                  3                     100        300
2                  1                     150        50
2                  2                     200        0
2                  3                     100        150
2                  4                     50          300
3                  1 and so on...

Any help would be greatly appreciated!
sandu
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