*** deal with missing values *** replace wt = . if wt > 80 replace ht = . if ht > 800 replace arm = . if arm > 80 ***generate obs num representing equally spaced times**** egen newid=group(id) summ newid drop id ren newid id sort id age by id: gen obsno=_n tab obsno tsset id obsno ** OLS ** reg arm wt age sex xi:reg arm wt age i.sex ** uniform corr ** xtreg arm wt age sex, re ** exponential corr ** prais arm wt age sex xtgls arm wt age sex, igls corr(ar1) i(id) force ** uniform + exponential ** xtregar arm wt age sex