[R] (Censboot, Z-score, Cox) How to use Z-score as the statistic within censboot?

[David Lloyd]

Dear R Help list,

My question is regarding extracting the standard error or Z-score from a
cph or coxph call. My Cox model is: -

modz=cph(Surv(TSURV,STATUS)~RAGE+DAGE+REG_WTIME_M+CLD_ISCH+POLY_VS,
data=kidneyT,method="breslow", x=T, y=T)

I've used names(modz) but can't see anything that will let me extract
the Z scores for each coefficient or the standard errors in the same way
one can use coef (modz).

I need to get either the se or Zscore as I am hoping to be able to use
the Zscore within a statistic function used in censboot. I wish to find
the proportion of times each of the variables in the cox model are
significant out of the R=1000 bootstrap resamples.

My current function for us with the bootstrap only gives me the
coefficients: - 

func=function(kidneyT,indices)
{

kidneyT=kidneyT[indices,]
modz=coxph(Surv(TSURV,STATUS)~RAGE+DAGE+REG_WTIME_M+CLD_ISCH+POLY_VS,dat
a=kidneyT,method="breslow")

coefficients(modz)

}


I would like to be able to modify the following code so modz.cens.boot$t
below gives me an array of the Z-scores for each variable and each
resample - not the coefficients

modz.cens.boot=censboot(kidneyT, func,R=1000,sim="ordinary")
modz.cens.boot


I hope this is clear enough? I'm still getting to terms with the
Bootstrap, having only just started trying to use it a few days ago.

Any help on this would clear a massive headache for me as I've been
going around in circles for hours and hours on this.

Thx 

DaveL





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