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 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


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http://mail.nana.co.il

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