Good afternoon,
I am currently trying to do some work on survival analysis.
- I hope to seek your advice re: 2 questions (1 general and 1 specific)
(1) I'm trying to do a stratified Cox analysis and subsequently plot(survfit(object)). It seems to work for some strata, but not for others.
I have tumor grade, which is a range of 1 - 4.
When I divide this range of 1:4 into 2 groups, it works fine for strata(grade>2) and strata(grade > 3). However, if I do a strata(grade>1), there is an error when I do a survfit( <coxph object> )
Call: survfit.coxph(object = s)
Error in print.survfit(structure(list(n = as.integer(46), time = c(22, : length of dimnames [1] not equal to array extent
(2) As a general question, is it possible to distinguish between confounding and interaction in the Cox proportional hazards model?
Thanks!
Min-Han
The Design package provides another way to use the survival package.
library(Design) # also issues library(Hmisc) so need to install both
d <- datadist(mydataframe); options(datadist='d')
f <- cph(Surv(...) ~ ... + strat(z), surv=TRUE) # note strat instead of strata
survplot(f, z=vector of strata values to plot survival curves for)
survplot has many options
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
