[R] Defining reference category for a cph model summary inside of a "for" loop

From: Wells, Brian <WELLSB_at_ccf.org>
Date: Fri, 28 Mar 2008 13:48:25 -0400


I have the following code.    

> f <- cph(formula = Surv(TimeToDeath, Dead == "Yes")
~1,data=single.dat, x=T, y=T, surv=T)

> for(i in c('A', 'B', 'C', 'D', 'E', 'F')){

> f <-update(f,as.formula(paste('Surv(TimeToDeath, Dead ==
"Yes")~',i,sep='')))

> print(summary(f, paste(i,"=1st Quartile", sep='')))
   

There is no error message generated in R, but R ignores the reference category defined with paste in the summary function for the cph model.  

The output uses the "1st Quartile" as the reference category to calculate hazards for some of the variables defined by i, but not all of them.    

Any help would be greatly appreciated.  

thanks  

Brian J. Wells, MD, MS

Research Associate

Quantitative Health Sciences

Cleveland Clinic    


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