reshape with combination

[River Huang]

Dear All, I found this question here (in Chinese). The dataset is:

* Example generated by -dataex-. For more info, type help dataex
clear
input float id str4 x
1 "a"
1 "b"
1 "c"
2 "a"
2 "b"
end

and the desired result is:

* Example generated by -dataex-. For more info, type help dataex
clear
input float id1 str4(x1 x2)
1 "a" "b"
1 "a" "c"
1 "b" "c"
2 "a" "b"
end

Within each `id', use the elements in `x' to form different combinations in `x1' and `x2'. Any suggestions are highly appreciated.

[Andrew Musau]

* Example generated by -dataex-. For more info, type help dataex
clear
input float id str4 x
1 "a"
1 "b"
1 "c"
2 "a"
2 "b"
end

preserve
rename x x2
tempfile b
save `b'
restore
joinby id using `b'
keep if x<x2

Res.:

. l

     +-------------+
     | id   x   x2 |
     |-------------|
  1. |  1   a    c |
  2. |  1   a    b |
  3. |  1   b    c |
  4. |  2   a    b |
     +-------------+

[River Huang]

Dear Andrew, Thanks a lot for this helpful suggestion.