[R] coxph and robust variance estimation

["Sven Knüppel"]

Hello,

I would like to compare two different models in the framework of Cox proportional hazards regression models.

On Rsitesearch and google I don't find a clear answer to my question.

My R-Code (R version 2.9.0)

coxph.fit0 <- coxph(y ~ z2_ + cluster(as.factor(keys))+ strata(stratvar_),
    method="breslow" ,robust=T  )
    
coxph.fit1 <- coxph(y ~ z_ + cluster(as.factor(keys))+ strata(stratvar_),
  method="breslow" ,robust=T  )  # marker and covariates

# Analysis of Devaince table
coxph.aov <- anova(coxph.fit0 , coxph.fit1, test="Chisq")

In the single models coxph.fit0 and coxph.fit1 I can use a robust variance estimation.
It seems that the function anova don't use a robust estimation for the analysis of deviance.

My question is, how can I use robust estimation for the analysis of deviance?

With kind regards,

Sven Knüppel
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