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##############################################
# Section 9.4 Survival Modeling
##############################################
library(LearnBayes)
data(chemotherapy)
attach(chemotherapy)
library(survival)
survreg(Surv(time,status)~factor(treat)+age,dist="weibull")
start=c(-.5,9,.5,-.05)
d=cbind(time,status,treat-1,age)
fit=laplace(weibullregpost,start,d)
fit
proposal=list(var=fit$var,scale=1.5)
bayesfit=rwmetrop(weibullregpost,proposal,fit$mode,10000,d)
bayesfit$accept
par(mfrow=c(2,2))
sigma=exp(bayesfit$par[,1])
mu=bayesfit$par[,2]
beta1=bayesfit$par[,3]
beta2=bayesfit$par[,4]
hist(beta1,xlab="treatment",main="")
hist(beta2,xlab="age",main="")
hist(sigma,xlab="sigma",main="")
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