Re: [R] Survival dummy variables and some questions

From: Stephen <szlevine_at_nana.co.il>
Date: Tue 19 Jul 2005 - 01:36:44 EST

Hi 1. To clarify: There is a posting saying that dummy regression using the coxph function is not possible... That posting may be outdated.... 2. Q. You say 'Make sure that eventbefore is a "pre time zero" measurement' please explain: Do you mean that if someone who is not left censored and has no eventbefore then their value is zero? So John is in my study from 1978 to 1992 and has no events prior to 1980 then John's eventbefore is 0 prior to 1980. 3. .... just kidding... Thanks S ----- Original Message ----- From: "Frank E Harrell Jr" To: "Stephen" Cc: Sent: Monday, July 18, 2005 2:46 PM Subject: Re: [R] Survival dummy

variables and some questions > Stephen wrote: >> Hi All, >> >> I am
currently conducting some survival analyses. I would like to >> extract
coefficients at each level of the IVs. I read on a previous >> posting
that dummy regression using coxph was not >> possible. > > I'm not sure what that means. > >> >> Therefore I though, hey why not categorize the variables (I realize some >> folks object to categorization but the
paper I am >> replicating appears to have done so ...) > > The fact that
some people murder doesn't mean we should copy them. And > murdering
data, though not as serious, should also be avoided. > > Make sure that
eventbefore is a "pre time zero" measurement. > > Frank > >> >> and turn the variables into factors and then try the analysis. >> >> E.g., Dataset <- read.table("categ.dat", header=TRUE) >> >> Dataset$eventbefore2c <- factor(Dataset$eventbefore) >> >> .. other IVs here >> >> ... >> >> surv.mod1 <- coxph(Surv(start, stop, event) ~ sex2 + ageonset2c + >> eventbefore2c + daysbefore2c, data=Dataset) >> >> Strangely enough, I receive a warning message when the variables are >> treated in this way: X matrix deemed to be singular; variable 11 in: >> coxph(Surv(start, stop, event) ~ sex2 + ageonset2c + eventbefore2c + I
>> don't receive any warnings just treating the variables in their >>
initial continuous format. >> >> I am currently using version >> >>
platform i386-pc-mingw32 >> >> arch i386 os mingw32 system i386, mingw32

>> status major 2 minor 1.1 >> year 2005 month 06 day 20 >> language R
Is this approach to dummy variable using coxph erroneous? >> >> Is there
another way to conduct dummy variable regression with coxph? >> >> Also,
if I include frailty (id) does anyone know of a useful way to >>
investigate frailty? >> >> If one were to plot recurrent events does anyone know of a way of >> interpreting them? >> >> References & code appreciated. >> >> BTW. not too familiar with R, less so with survival analysis .... but >> well worth the effort. >> >> Many thanks in advance... >> >> Regards >> >> Stephen >> >> >> ???? ?"? ???? ???? >> http://mail.nana.co.il >> >> [[alternative HTML version deleted]] >> >>
>> >>


>> >> ______________________________________________ >>
R-help@stat.math.ethz.ch mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide! >> http://www.R-project.org/posting-guide.html > > > -- > Frank E Harrell Jr Professor and Chair School of Medicine > Department of Biostatistics Vanderbilt University >

???? ?"? ???? ????
http://mail.nana.co.il

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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Jul 19 00:40:56 2005

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