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.
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 ...)
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 dont 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
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http://mail.nana.co.il
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