Hi, in coxph, coxph(Surv(time, status)~x,data=alm). How to encode x? For example, if x has two groups, the treatment group and control group. if I encode them as 1 and 2. Is the HR results treatment/control? What if I encode them as 0 and 1. I am confused with how survival package works for HR. What should I do to get a treatment/control HR? Thank you. -- View this message in context: http://r.789695.n4.nabble.com/need-help-with-understanding-coxph-encoding-tp4367514p4367514.html Sent from the R help mailing list archive at Nabble.com.
need help with understanding coxph encoding
2 messages · summer, David Winsemius
On Feb 7, 2012, at 9:11 PM, summer wrote:
Hi, in coxph, coxph(Surv(time, status)~x,data=alm). How to encode x? For example, if x has two groups, the treatment group and control group. if I encode them as 1 and 2. Is the HR results treatment/control? What if I encode them as 0 and 1. I am confused with how survival package works for HR. What should I do to get a treatment/ control HR?
The proper way would be to construct "x" is as a factor. Then you will not be implicitly telling the function that it is dealing with a numeric value. (In this simple case it probably doesn't really matter. The coefficient for the effect would be the same.
David Winsemius, MD West Hartford, CT