Generating a Fixed Effect for Pairs

[Sydney Hibbs]

Hi All,

I am dealing with FIPS code pairs. I would like to generate a fixed effect variable that matches the pairs. Please see an example below, that I would like my data to look like.

FIPS	FIPS2	County-Pair Fixed Effect
1001	1021	1
1021	1001	1
1011	1005	2
1005	1011	2
1013	1035	3
1007	1105	4
1035	1013	3
1105	1007	4
1005	1067	5

Thanks!

[Clyde Schechter]

egen country_pair = group(fips fips2)

[Sydney Hibbs]

Thank you for your comment. I tried using the code above and unfortunately it does not recognize pairs across columns. Do you have a suggestion for generating a variable across the two columns? Cheers

[Clyde Schechter]

Oh, I see. You want 1001 1021 to be the same pair as 1021 1001. You even showed that in your example, but I didn't notice it. Sorry.

gen c1 = min(fips, fips2)
gen c2 = max(fips, fips2)
egen county_pair = group(c1 c2)

list, noobs clean

[Sydney Hibbs]

Hi Clyde,

Thank you for your response! That worked!

I also was able to generate a fixed effect using the code below, for anyone else who is interested in an alternative (yet more difficult) way of doing this:

set more off
levelsof FIPS1, local(F1)
levelsof FIPS2, local(F2)

gen count=0
gen pair=.
foreach f1 of local F1 {
foreach f2 of local F2 {
replace pair=count+1 if (FIPS1==`f1' & FIPS2==`f2') | (FIPS1==`f2' & FIPS2==`f1')
replace count=count+1
}
}