[R] What's the baseline model when using coxph with factor variables?

David Winsemius dwinsemius at comcast.net
Thu Dec 1 18:35:42 CET 2011

On Dec 1, 2011, at 12:00 PM, Andreas Schlicker wrote:

> Hi all,
> I'm trying to fit a Cox regression model with two factor variables  
> but have some problems with the interpretation of the results.  
> Considering the following model, where var1 and var2 can assume  
> value 0 and 1:
> coxph(Surv(time, cens) ~ factor(var1) * factor(var2),  data=temp)
> What is the baseline model? Is that considering the whole population  
> or the case when both var1 and var2 = 0?

This has been discussed several times in the past on rhelp. My  
suggestion would be to search your favorite rhelp archive using   
"baseline hazard Therneau", since Terry Therneau is the author of  
survival. (The answer is closer to the first than to the second.)

> Kind regards,
> andi
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David Winsemius, MD
West Hartford, CT

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