### survival function for the lifetimes of guinea pigs - Example A p.381

library(survival)

# c1 lifetime c2 status c3 group

gpig = matrix(scan("C:\\Users\\Eric A. Suess\\Desktop\\gpig1.dat"),ncol=3,byrow=T)

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

dimnames(gpig) 

gpig.data = data.frame(gpig)

gpig.data

gpig.data$time
gpig.data$status
gpig.data$group

fit = survfit(Surv(time, status) ~ 1, data=gpig.data)
X11()
plot(fit)

# plot the survival functions for the groups on the same plot, Kaplan-Meier

fit = survfit(Surv(time, status) ~ group, data=gpig.data)
X11()
plot(fit, lty = 1:6, xlab="Days elapsed",ylab="Proportion of live animals")
summary(fit)

# comparing Kaplan-Meier Survival Curves

survdiff(Surv(time, status) ~ group, data = gpig.data)

# Fit an exponential model

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