On Jun 28, 2011, at 6:51 AM, Jacob Brogren wrote:
Hi,
I ran the example on pp. 799-800 from Machael Crawley's "The R Book"
using package survival v. 2.36-5, R 2.13.0 and RStudio 0.94.83. The
model is a Cox's Proportional Hazards model. The result was quite
different compared to the R Book. I have compared my code to the
code in the book but can not find any differences in the function
call. My results are attached as well as a link to the results
presented in the book (link to Google Books).
Shouldn't this instead go to Mr Crawley? Despite his unfortunately
successful efforts to give the impression that his book is
authoritative and somehow official, it is neither. I have never seen a
contribution to the R effort from Mr. Crawley.
--
David.
When running the examples on pp. 797-799 I can't detect any
differences in results so I don't think there are errors in the data
set or in the creation of the status variable.
---------------------------------
Original from the R Book:
http://books.google.com/books?id=8D4HVx0apZQC&lpg=PA799&ots=rQgd_8ofeS&dq=r%20coxph%20crawley&pg=PA799#v
=onepage&q&f=false
---------------------------------
My result:
summary(model1)
Call:
coxph(formula = Surv(death, status) ~ strata(cohort) * gapsize,
data = seedlings)
n= 60, number of events= 60
coef exp(coef)
se(coef) z Pr(>|z|)
gapsize -0.001893 0.998109 0.593372
-0.003 0.997
gapsize:strata(cohort)cohort=September 0.717407 2.049112
0.860807 0.833 0.405
exp(coef) exp(-coef) lower .95
upper .95
gapsize 0.9981 1.002
0.3120 3.193
gapsize:strata(cohort)cohort=September 2.0491 0.488
0.3792 11.074
Rsquare= 0.022 (max possible= 0.993 )
Likelihood ratio test= 1.35 on 2 df, p=0.5097
Wald test = 1.32 on 2 df, p=0.5178
Score (logrank) test = 1.33 on 2 df, p=0.514
Anyone have an idea why this is occurring?
Kind Regards
Jacob
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
