I want to find the summation of unique rf_id for each unique county in different years of my dataset. Is the following going to suffice ?

Code:
bysort rf_id county (year) : gen wanted = _n == 1
bysort rf_id (year county): replace wanted = sum(wanted)
by county year: replace wanted = wanted[_N]


Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input long rf_id float(year county)
102990885 2000 13121
103020981 2000 36061
103070511 2001 36061
103090560 2000  9009
103100020 2001 9009
103100550 2000 41051
103100882 2002 9009
103100885 2000  6081
103120813 2001 48113
103170821 2000  4013
103180001 2001  6075
103180015 2001 51013
103180097 2000 10003
103200783 2000     .
103210207 2000 36061
103270266 2000 17031
103340240 2000 9009
103360009 2000  6037
103360119 2000  6037
103390422 2000 48201
103400270 2000 24031
103400773 2000 36061
103400785 2000 27053
103400808 2000  8031
103400829 2000  8031
103400840 2000  6075
103430018 2000  6085
103430187 2002 24031
103460235 2000 11001
103470580 2001 11001
103480485 2000  6059
103480531 2000 17031
103490132 2001  8031
103490362 2000 36061
103510154 2001 36061
103510160 2002 36061
103510293 2000 27053
end