st: Incorporating time varying variable into discrete time model

[Mike <quangdata@gmail.com>]

Hi all:

There are discussions about Cox model about integrating time varying
variables into a continous time model , but seem not any on discrete
time model. I would like to ask whether you know something about that.
For example, if "age at migration" is a time varying variable, since
the age increases as the duration increases. But then how to caputre
such varying effects in the model.
I have already expanded data with the following commands:
ge id=_n;
lab var id "subject identifier";
*qui list id migmonth;
expand migmonth;
bysort id: ge seqvar=_n;
lab var seqvar "spell month identifier, by subject";
bysort id: ge returnee=mig==3 & _n==_N;
lab var returnee "binary depvar for discrete hazard model";
ge logd=ln(seqvar);
ge seqvar2=seqvar^2;
ge seqvar3=seqvar^3;
lab var logd "ln(t)";
ltable migmonth rom;
ltable migmonth rom,graph title("Survivor function,migration duration(ltable)");
ltable migmonth rom,hazard;
My current estimation commad(without the time-varying variables) is:
pgmhaz logd age marriage sex yedu hhsize num_16 wage_occup log_gdp
num_rm_v num_rm_h job_ch_mig, id(id) s(seqvar) d(returnee);

Thanks a lot!
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