Dear useRs,
I am trying to fit a Cox PH model on survival data from a lung cancer
dataset. I would like to include the patient staging (I-IV) as a
covariate. For this I use the following function:
coxph(Surv(time,status) ~ stage)
The staging information is a categorical variable, and it is important
to take the ordering into account (I<II<III<IV). Does the coxph function
handle correctly ordered factors, or is it preferable to recode the
covariate into numerical values (1-4)?
Thank you very much for your help,
Florent
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Dr Florent BATY
Pulmonary Gene Research, Universitätsspital Basel
Petersgraben 4, CH-4031 Basel, Switzerland
tel: +41 61 265 57 27 - fax: +41 61 265 45 87
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