##### Survival analysis ######################
#####  Parametric model ######################

library(survival)
library(MASS)
ovarian  ###Ovarian Cancer Survival Data###
attach(ovarian)

###Weibull regression#######
fit1=survreg(Surv(futime, fustat)~age+resid.ds+rx+ecog.ps, dist="weibull", data=ovarian)
aic1=AIC(fit1)
bic1=BIC(fit1)

###Loglogistic regression#####
fit2=survreg(Surv(futime, fustat)~age+resid.ds+rx+ecog.ps, dist="loglogistic", data=ovarian)
aic2=AIC(fit2)
bic2=BIC(fit2)

###Lognormal regression#####
fit3=survreg(Surv(futime, fustat)~age+resid.ds+rx+ecog.ps, dist="lognormal", data=ovarian)
aic3=AIC(fit3)
bic3=BIC(fit3)

fit4=survreg(Surv(futime, fustat)~age+resid.ds+rx+ecog.ps, dist="exponential", data=ovarian)
aic4=AIC(fit4)
bic4=BIC(fit4)

aic=c(aic1,aic2,aic3,aic4)
aic

bic=c(bic1,bic2,bic3,bic4)
bic

###Both AIC and BIC indicate that lognormal is the selected model############