Hi All,

I am working in the 'survival' library and need to know how to code a
variable time interaction for left truncated data (not all subjects
followed from the start of the study). I therefor add in the entry time and
exit time variables into the formula.

Here is my basic formula

    CSHR.shore.fly <- coxph(Surv(entry, exit, to == 1) ~ shore.cat, data
      glba.mod)

My variable shore.cat is violating the proportional hazards assumption so I
am trying to add in an interaction with time. Do I interact exit? entry? or
the range of the two?

Thanks, Tim

-- 
Tim Marcella
508.498.2989
timmarcella@gmail.com

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