Re: st: How to expand the data using set-variables

[Christopher Baum <kit.baum@bc.edu>]

<>
On Oct 24, 2010, at 2:33 AM, Badri wrote:

> I have a global tariff data that contains observations corresponding
> to sectors (defined by variable sec), exporters (defined by variable
> exp) and importers (defined by variable imp). Both exp and imp are
> sets, but defined in numbers.
> 
> While there is data for all observations corresponding to exp and imp
> elements that are not identical ( exp!=imp), there are no observations
> where exp==imp. Now I want to expand the data by a number of
> observations that have exp==imp. I know the number of observations
> required to do this. Is there any way I can do this in stata? Mata
> programming or other simpler ways?

clear
set obs 100
g expno = ceil(_n/10) 
g impno = mod(_n,10)+1
g fakeflow = runiform()*100
drop if expno == impno
sort expno impno
// data now contain exp-imp pairs lacking those with exp==imp
expand 2, gen(newobs)
egen tt = tag(expno) if newobs
drop if newobs & !tt
replace fakeflow = . if newobs
replace impno = expno if tt
sort expno impno
// data should now contain records for exp==imp with missing values for fakeflow
list

Kit Baum   |   Boston College Economics & DIW Berlin   |   http://ideas.repec.org/e/pba1.html
                              An Introduction to Stata Programming  |   http://www.stata-press.com/books/isp.html
   An Introduction to Modern Econometrics Using Stata  |   http://www.stata-press.com/books/imeus.html


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