library(survival)

attach(aml)

rm(time) ; rm(x) ; rm(status)

data.frame(time,status,x)

Surv(time[x=="Maintained"],status[x=="Maintained"])
Surv(time[x=="Nonmaintained"],status[x=="Nonmaintained"])

aml.maint <- Surv(time[x=="Maintained"],status[x=="Maintained"])
aml.nonmt <- Surv(time[x=="Nonmaintained"],status[x=="Nonmaintained"])

print(survfit(aml.maint),show.rmean=T)
print(survfit(aml.nonmt),show.rmean=T)

par(mfcol=c(1,2))
plot(survfit(aml.maint),main="Maintained")
plot(survfit(aml.nonmt),main="Non-maintained")

par(mfcol=c(1,1))
plot(survfit(aml.maint,conf.type="none"))
lines(survfit(aml.nonmt),lty=2)