### survival function for the survival times of hepetitis patients

hepa = matrix(scan("C:\\Users\\Eric A. Suess\\Desktop\\hepatitis.dat"),ncol=3,byrow=T)

dimnames(hepa) = list(NULL, c("time","status","group"))		# dimnames fills names row by cols

dimnames(hepa) 

hepa.data = data.frame(hepa)

hepa.data

hepa.data$time
hepa.data$status
hepa.data$group

fit = survfit(Surv(time, status) ~ 1, data=hepa.data)
plot(fit)

# plot the survival functions for the hepatitis data, Kaplan-Meier

fit = survfit(Surv(time, status) ~ group, data=hepa.data)
plot(fit, lty = 1:6, xlab="Weeks elapsed",ylab="Proportion of live patients")
summary(fit)

# Fit an exponential model

fit.exp = survreg(Surv(time, status) ~ group, data = hepa.data, dist="exponential")
summary(fit.exp)