spider.time<-c(20,22,29,32,40,42,44,46,51,57,
                21,30,31,45,55,58,73,81,105,107)
 spider.spec<-c(rep("jump",10),rep("crab",10))
 spider.icrab<-as.numeric(spider.spec=="crab")
 spider.status<-rep(1,20)
 spider.df<-data.frame(etime=spider.time,species=spider.spec,
                      status=spider.status,icrab=spider.icrab)

 summary(coxph(Surv(etime)~icrab,data=spider.df))
 coxph(formula = Surv(etime) ~ icrab, data = spider.df)


   n = 20

        coef exp(coef) se(coef)     z     p
 icrab -1.25     0.288     0.57 -2.19 0.029

       exp(coef) exp(-coef) lower .95 upper .95
 icrab     0.288       3.48    0.0942     0.878

 Likelihood ratio test= 5.18  on 1 df,   p=0.0228
 Wald test            = 4.79  on 1 df,   p=0.0287
 Efficient score test = 5.31  on 1 df,   p=0.0212