Hi,

I wanted to do the cox model using a matrix. The following lines illustrate what I want to do:
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dat <- matrix(rnorm(30), ncol=3,dimnames = list(1:10,letters[1:3]))
Survival <- rexp(10)
Status <- ifelse(runif(10) < .7, 1, 0)
mat <- as.data.frame(cbind(dat,Survival,Status))

cmod <- coxph(Surv(Survival, Status) ~ a+b+c, mat)
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This works fine. However, I need to change the code so that the column headers ( a+b+c )are passed into the coxph function on the fly. What string/object do I need to generate so the function works? I am trying:

# For example
chead <- "a+b+c"
cmod <- coxph(Surv(Survival, Status) ~ chead, mat)
but this gives an error since I'm passing in a string. Can I change chead to something so that the code works?
many thanks.


      
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