Ying,
Is this what you are looking for?:
---------------------------------
clear
input id
4001
4001
4001
4002
4002
4003
4003
4003
4003
4004
4004
4004
4008
4172
4172
end
bysort id: generate nobs=_n
bysort id: generate totobs=_N
list
------------------------------
Good luck,
Svend
________________________________________________________
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C, Denmark
Phone, work: +45 8942 6090
Phone, home: +45 8693 7796
Fax: +45 8613 1580
E-mail: [email protected]
_________________________________________________________
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