I have a dataset where subjects (id) are followed in one of two time periods
(or both time periods) and at some point die or are censored. The data is
arranged as multiple records per subject. For example
id group StartTime EndTime outcome
1 0 0 350 0
1 1 350 500 1
2 0 0 200 0
2 1 200 600 1
3 1 0 300 0
When I use stset such as
stset EndTime, id(id) time0(StartTime) failure(outcome)
I get data like:
id group StartTime EndTime outcome _t _t0
1 0 0 350 0 350 0
1 1 350 500 1 500 350
2 0 0 200 0 200 0
2 1 200 600 1 600 200
3 1 0 300 0 300 0
which looks appropriate, but when I try to graph a KM curve of the second
time period (group==1) with
sts graph if group==1
I get 600 days worth of time, even though the maximum time anyone spends in
the group 1 time period is 400 days.
A colleague's suggestion was to treat each record like an individual
subject, dropping the 'id(id)' parameter from the STSET command, but my
understanding of the Stata's survival analysis was that it should be able to
handle multiple records per subject. I've reviewed the manuals and the books
"Introduction to Survival Analysis using Stata" and have been unable to
figure this out.
If this is a problem with the KM curves, did it also occur with my 'stcox if
group==1' commands?
Sorry for the long explanation, but any help would be greatly appreciated.
Thanks,
Shawn
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