> I'm struggling with a data manipulation problem: I have a dataset with
> list of observations on a string variable and want to create pairwise
> combinations. My dataset looks like this:
>
> country1
> A
> B
> C
>
> I need the possible combinations so that the new dataset looks like
>
> country1 country2
> A B
> A C
> C B
>
> I could take the same list in two different datasets and then use the
> command "cross", but that gives me 3! combinations:
>
> AB AC BA BC CA CB
>
> For my purposes, AB and BA are identical. How do I create the list?
If you have numeric IDs of your countries, then you can clean up the
duplicates by something like
keep if id1>id2
You can create those numeric IDs by something like
gen id = _n
if observations are unique, or by
egen id = group(country)
if they are not.
--- Stas Kolenikov
-- Ph.D. student in Statistics at UNC-Chapel Hill
- http://www.komkon.org/~tacik/ -- [email protected]
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