-egen, total()- (formerly -sum()-) just ignores 
missings. 
The problem with -collapse- is that you have no 
way of relating the results to the original dataset. 
It solves the problem as posed, but at a price. 
Nick 
[email protected] 
Dimitriy V. Masterov
 
> Try
> 
> bys id: egen type=sum(vi) if vi~=.
> collapse type, by(id)
> 
> This will count people with missing observations as "." and not zero,
> and it will avoid double-counting.
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