wbc
| white blood count |
ag
|
a test result, "present" or "absent"
|
time
| survival time in weeks |
Feigl, P. & Zelen, M. (1965) Estimation of exponential survival probabilities with concomitant information. Biometrics, 21, 826-838.
library(survival4) data(leuk) attach(leuk) plot(survfit(Surv(time) ~ ag), lty=c(2,3)) # now Cox models leuk.cox <- coxph(Surv(time) ~ ag+log(wbc)) summary(leuk.cox)