cancer<-read.table("cancer.txt",header=T)
attach(cancer)
names(cancer)
plot(survfit(Surv(death,status)~treatment),lty=c(1,2,3,4))
tapply(death[status==1],treatment[status==1],mean)
tapply(death[status==1],treatment[status==1],var)
model<-survreg(Surv(death,status)~treatment,dist="exponential")

model<-survreg(Surv(death,status)~treatment,dist="extreme")
summary(model)
