how to use "pairdata" with duplicate "ind"

[liu sally]

hello everyone,
I'm trying to use "pairdata" for the first time and found a question: my individualID variable is not unique
the example dataset looks like:

input int (year city ind X Y)
1 1 1 0.3 321
1 1 2 0.7 452
1 2 3 0.8 879
1 2 4 0.6 897
1 3 5 0.9 356
1 3 6 0.5 698
end

I hope the dataset would look like this:

input int (year city ind X Y) str5 pair
1 1 1 0.3 321 "(1,2)"
1 1 2 0.7 452 "(1,2)"
1 2 3 0.8 879 "(1,2)"
1 2 4 0.6 897 "(1,2)"
1 1 1 0.3 321 "(1,3)"
1 1 2 0.7 452 "(1,3)"
1 3 5 0.9 356 "(1,3)"
1 3 6 0.5 698 "(1,3)"
1 2 3 0.8 879 "(2,3)"
1 2 4 0.6 897 "(2,3)"
1 3 5 0.9 356 "(2,3)"
1 3 6 0.5 698 "(2,3)"
end

(Real dataset has many years, the example just listed one)

I try to use "pairdata X Y, ind(city) fam(year)", it doesn't work because the variable "city" is duplicate.

Any help would be immensely appreciated! Thank you!

[Andrew Musau]

clear
input int (year city ind X Y)
1 1 1 0.3 321
1 1 2 0.7 452
1 2 3 0.8 879
1 2 4 0.6 897
1 3 5 0.9 356
1 3 6 0.5 698
2 1 1 0.3 321
2 2 3 0.8 879
2 2 4 0.6 897
2 3 6 0.5 698
end

preserve
keep city year
contract *
rename city city2
tempfile 2
save `2'
restore
joinby year using `2'
drop if city==city2
gen pairid= string(min(city, city2)) +","+ string(max(city, city2))
drop _freq city2

Res.:

. sort year pairid ind

. l, sepby(year pairid)

     +--------------------------------------+
     | year   city   ind   X     Y   pairid |
     |--------------------------------------|
  1. |    1      1     1   0   321      1,2 |
  2. |    1      1     2   0   452      1,2 |
  3. |    1      2     3   0   879      1,2 |
  4. |    1      2     4   0   897      1,2 |
     |--------------------------------------|
  5. |    1      1     1   0   321      1,3 |
  6. |    1      1     2   0   452      1,3 |
  7. |    1      3     5   0   356      1,3 |
  8. |    1      3     6   0   698      1,3 |
     |--------------------------------------|
  9. |    1      2     3   0   879      2,3 |
 10. |    1      2     4   0   897      2,3 |
 11. |    1      3     5   0   356      2,3 |
 12. |    1      3     6   0   698      2,3 |
     |--------------------------------------|
 13. |    2      1     1   0   321      1,2 |
 14. |    2      2     3   0   879      1,2 |
 15. |    2      2     4   0   897      1,2 |
     |--------------------------------------|
 16. |    2      1     1   0   321      1,3 |
 17. |    2      3     6   0   698      1,3 |
     |--------------------------------------|
 18. |    2      2     3   0   879      2,3 |
 19. |    2      2     4   0   897      2,3 |
 20. |    2      3     6   0   698      2,3 |
     +--------------------------------------+