try
res <- coxph(Surv(TIME, STATUS)~TREAT, data=leukemia, method="breslow")
R default for handling ties is Efron's method, whereas it's Breslow for
STATA.
Have a look under method in ?coxph it clearly states this, and STATA
output clearly states the Breslow method for ties in the output of
running a cox model.
HTH
Gary
---------------------------------------------------------------
Dr Gary S Collins Tel: +44 (0)1865 284418
Centre for Statistics in Medicine Fax: +44 (0)1865 284424
Wolfson College Annexe www.csm-oxford.org.uk
University of Oxford
Linton Road
Oxford, OX2 6UD
---------------------------------------------------------------
Michel Boutsen wrote:
Hello
I would like to develop the use of R.
Trying R and more particulary the cox model, I am surprised by discrepancies
between results with stata and R for a cox model
With the same data base, I get a hazard ratio (4.82) that is not the same
obtained with stata (4.52)
You will find attached the file leukemia.dta I used (Stata)
Here are the codes for R
leukemia=read.fwf(file="leukem.txt",widths=c(4,2,3,2,5,2),col.names=c("id","TREAT","TIME","STATUS","LOGWBC",
"GENDER"))
library(survival)
res <- coxph(Surv(TIME, STATUS)~TREAT, data=leukemia)
summary(res)
and here the codes for for stata
infix ID 2-3 TREAT 6 TIME 8-9 STATUS 11 LOGWBC 12-16 GENDER 18 using
"g:rleukem.txt",clear
stset TIME, failure(STATUS==1)
stcox TREAT
SPSS and EPIinfo give the same HR than Stata
I tried with an other database without any problem
What would be the problem??? I changed of pc and versions of R (2.81 & 2.9.0)
without any change. The means are the same for the two packages.
I saw a few posts with discrepancies but not with the same database
Thanks in advance
Michel Boutsen
Brussel's University
Department of Biostatistics
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