Hi,
I am computing the Nelson-Aalen (NA) estimate of baseline cumulative hazard in
two different ways using the "survival" package. I am expecting that they
should be identical. However, they are not. Their difference is a
monotonically increasing with time. This difference is probably not large to
make any impact in the application, but is annoyingly non-trivial for me to
just ignore it.
This is a competing risks problem, with the Green & Byar (1980) data set (the
STATA data set is attached).
Can anyone explain to me the reason for the discrepancy?
require(foreign)
gb <- read.dta("GB.dta") # Green & Byar data; N = 483
# Method 1
fit1 <- coxph( Surv(time, status=="Cancer" | status=="CVD" | status=="Other") ~
1, data=gb)
h1 <- basehaz(fit1)
# Method 2
fit2 <- survfit(Surv(time, status=="Cancer" | status=="CVD" | status=="Other")
~ 1, data=gb)
jump <- fit2$n.event > 0
h2 <- cumsum(fit2$n.event[jump]/fit2$n.risk[jump])
plot(h1$time, h1$hazard - h2)
Thank you,
Ravi.
____________________________________________________________________
Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology
School of Medicine
Johns Hopkins University
Ph. (410) 502-2619
email: rvarad...@jhmi.edu
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
