How about:
by pref1 pref2, sort: replace wgt = sum(wgt)
by pref1 pref2: keep if _n == _N
regards
uli
Dietrich Dr�ner wrote:
> I need to aggregate the number of observations in my data set when they
> have identical values on two variables AND I need to sum up the values of a
> third variable so that it remains the same for the reduced data set. I will
> try to illustrate this and also describe the substantial problem:
>
> my initial data matrix looks like this:
>
> act wgt pref1 pref2
> 1 4 100 0
> 2 5 33 0
> 3 3 33 50
> 4 3 100 50
> 5 10 33 0
> 6 10 33 100
> 7 5 33 50
> 8 3 33 50
> 9 10 33 50
> 10 2 33 50
> 11 5 33 0
> 12 5 33 50
> 13 8 33 50
> 14 4 100 0
> 15 10 33 50
> 16 100 70
> 17 100 70
>
> sum 87
>
> The first variable is the number of my actors (the 15 EU member states plus
> the European Commission and the European Parliament). The second variable
> is the voting weights of the member states. The third and fourth variables
> are preferences of the actors in two dimensions. Many of the actors have
> identical preference profiles that I need to aggregate.
>
> The result of this aggregation should look like this:
>
> act wgt pref1 pref2
> 1 8 100 0
> 2 20 33 0
> 3 46 33 50
> 4 3 100 50
> 5 10 33 100
> 6 100 70
>
> sum 87
>
>
> How can I do this in Stata (7)?
>
> Thank you!
>
> Regards,
>
> Dietrich.
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Dietrich Dr�ner
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> D - 78467 Konstanz
>
> Tel. (+49) - 7531 - 698003
> Fax (+49) - 1212 - 522970813
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>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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>
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