# RE: st: RE: pairwise dummy variables

 From "Nick Cox" To Subject RE: st: RE: pairwise dummy variables Date Wed, 3 May 2006 13:06:57 +0100

```Presumably you have done the combinatorial
calculation that the number of variables
implied is acceptable to Stata and your
set-up.

Something like this might be what you want:

levelsof voter_id, local(voters)
tokenize "`voters'"
local nv : word count `voters'

forval i = 1/`nv' {
local I = `i' + 1
forval j = `I'/`nv' {
su vote if body_id == ``i'' & voter_id == ``j'', meanonly
gen byte vote_``i''``j'' = r(min)
}
}

You might need another underscore in the names
to disambiguate.

Nick
n.j.cox@durham.ac.uk

Serguei Kaniovski

> Thank you, but this is not quite what I need. I would like to compute
> the frequencies of occurrence of all possible pairs of the binary
> variable "vote". To begin with, for example, generate
> variables "vote_*"
> for each possible pair of "voters_id", such that that, e.g.,
> "vote_12"
> takes the value "1" if "voters_id" both have "vote=1", else
> zero, or NA
> if one of the voters in not on the body.
>
> body_id,voter_id,vote,vote_12,vote_13,vote_17,vote_19,vote_23,
> vote_27,vote_29,vote_37,vote_39,...
> 1,1,1,0,1,1,0,0,0,0,1,0
> 1,2,0,0,1,1,0,0,0,0,1,0
> 1,3,1,0,1,1,0,0,0,0,1,0
> 1,7,1,0,1,1,0,0,0,0,1,0
> 1,9,0,0,1,1,0,0,0,0,1,0
> 2,1,1,0,.,0,.,.,0,.,.,.
> 2,2,0,0,.,0,.,.,0,.,.,.
> 2,7,0,0,.,0,.,.,0,.,.,.
>
> and so on.

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```