This is a follow-up to a query that was posted regarding some problems that
emerge when running anova analyses for cox models, posted by Mathias Gondan:
Matthias Gondan wrote:
>* Dear List,*>**>* I have tried a stratified Cox Regression, it is working
>fine, except for*>* the "Anova"-Tests:*>**>* Here the commands (should work
>out of the box):*>**>* library(survival)*>* d = colon[colon$etype==2, ]*>* m =
>coxph(Surv(time, status) ~ strata(sex) + rx, data=d)*>* summary(m)*>* #
>Printout ok*>* anova(m, test='Chisq')*>**>* This is the output of the anova
>command:*>**>* *>>* Analysis of Deviance Table*>>* Cox model: response is
>Surv(time, status)*>>* Terms added sequentially (first to last)*>>**>>*
> Df Deviance Resid. Df Resid. Dev P(>|Chi|)*>>* NULL
> 929 5233.5 *>>* strata(sex) 0 929
> *>>* rx 2 927 5221.2 *>>*
>Warning message:*>>* In is.na(coef(fit)) :*>>* is.na() auf nicht-(Liste oder
>Vektor) des Typs 'NULL' angewendet*>>* *>**>* It should be possible to do
>Chi-Square-Tests in a stratified analysis, *>* right?*
We have run into the same problem. In particular, we are running stratified
coxph models, but we are not able to generate a Chisq probability for both
models.
> drop1(Model,test='Chisq')
Single term deletions
Model:
Surv(adjusted_days_60, Death_60_10) ~ strata(chol_60)
Df AIC LRT Pr(Chi)
<none> 7437.6
strata(chol_60) 0 8513.2 1075.6
As you can see, why is the probability of the Chisq - i.e., Pr(Chi) -
missing?
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