

   SSuurrvviivvaall TTiimmeess aanndd WWhhiittee BBlloooodd CCoouunnttss ffoorr LLeeuukkaaeemmiiaa PPaattiieennttss

   AArrgguummeennttss::

        wbc: white blood count

         ag: a test result, `"present"' or `"absent"'

       time: survival time in weeks

   FFoorrmmaatt::

        A data frame with columns:

   DDeessccrriippttiioonn::

        A data frame of data from 33 leukaemia patients.

   SSoouurrccee::

        Cox, D. R. and Oakes, D. (1984) Analysis of Survival
        Data, Chapman  Hall, p. 9.  Taken from

        Feigl, P.  Zelen, M. (1965) Estimation of exponential
        survival probabilities with concomitant information.
        Biometrics, 21, 826-838.

   EExxaammpplleess::

        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)

