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