Eleni Rapsomaniki wrote:
I am using the package Design for survival analysis. I want to plot a
simple Kaplan-Meier fit of survival vs. age, with age grouped as
quantiles. I can do this:
survplot(survfit(Surv(time,status) ~ cut(age,3), data=veteran)
but I would like to do something like this:
survplot(survfit(Surv(time,status) ~ quantile(age,3), data=veteran)
#will not work
ideally I would like to superimpose estimates from cph models, which
automatically fit the 2nd to 4rth quantiles for age, so I need the age
groups to be grouped the same.
Any help greatly appreciated!
Eleni Rapsomaniki
This will result in a poor fitting model and residual confounding (by
only partially adjusting for a variable; you are assuming a piecewise
flat model). Use Surv( ) ~ strat(cut2(age,g=3)) ...
For Design it is often better to do
ageg <- cut2(age,g=3) # Donald Rumsfeld approach to using information
f <- cph(Surv( ) ~ strat(ageg), ...)
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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