[R] Weibull survival regression model with different shape parameters
therneau at mayo.edu
Sat Oct 3 15:46:58 CEST 2009
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I'm trying to fit a parametric survival model using the survreg function
with a Weibull distribution.
I'm studying the time to death of individuals from different families
and I would like to fit different shape parameters (ie 1/scale in R) for
each of the families. I looked it up in the help pdf and on the
internet, but I couldn't find anything.
Would it be possible to do such a thing ?
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Yes it is possible -- but clearly I need to add one more example to the help
page; use a strata() term.
> survreg(Surv(time, status) ~ ph.ecog + age + strata(sex), lung)
(Intercept) ph.ecog age
6.73234505 -0.32443043 -0.00580889
Loglik(model)= -1137.3 Loglik(intercept only)= -1146.2
Chisq= 17.8 on 2 degrees of freedom, p= 0.00014
n=227 (1 observation deleted due to missingness)
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