[R] Cox PH Warning Message

[Mayeul KAUFFMANN]

"Hi,
Can anybody tell me what the message below means and how to overcome it.
Thanks,
Neil
Warning message:
X matrix deemed to be singular; variable 2 in: coxph(Surv(age_at_death,
death) ~ project$pluralgp + project$yrborn +  ........."

Your 2nd covariate (yrborn) is colinear to the other covariates (or nearly
colinear). R drops it, but warns you. The results are OK.

Mayeul KAUFFMANN
Université Pierre Mendès France
Grenoble
France