infile id y time gender vita age  using a:\ichs.raw, clear

* fit MLE;

xi:glm y time age i.vita i.gender, fam(bin) link(logit)

* fit GEE
xi: xtgee y time age i.vita i.gender, fam(binomial) link(logit) corr(independent) i(id) t(time)

* fit the longitudinal model using different correlation structures;

xi: xtgee y time age i.gender i.vita, fam(bin) link(logit) corr(unstr) i(id) t(time) robust
xtcorr

xi:xtgee y time age i.gender i.vita, fam(bin) link(logit) corr(exch) i(id) t(time) robust
xtcorr

xi:xtgee y time age i.gender i.vita, fam(bin) link(logit) corr(ar 1) i(id) t(time) robust
xtcorr

log close;