Hi all,
I am a new BUGS user who is currently trying to reproduce the results for the Hepatitis B model in Chapter 2 of the book "Markov Chain Monte Carlo in Practice" by W.R.Gilks. However, I can't seem to be able to get the same results as in Fig. 2.4. Can anyone out there please tell me what did I do wrong or why can't I get similar results? Below is the BUGS program used for the model, the initials used, Fig. 2.4 (From the book) and my results. I have also included the data used for the model. Thanks in advance.
BUGS language for hep example (without gamma and y0[i]):
model
{
for( i in 1 : N ) {
for( j in 1 : T ) {
Y[i , j] ~ dnorm(mu[i , j],tau)
mu[i , j] <- alpha[i] + beta[i] * (t[i,j] - 6.5)
}
alpha[i] ~ dnorm(alpha0,tau.alpha)
beta[i] ~ dnorm(beta0,tau.beta)
}
tau ~ dgamma(0.01,0.01)
alpha0 ~ dnorm(0.0,0.0001)
tau.alpha ~ dgamma(0.01,0.01)
beta0 ~ dnorm(0.0,0.0001)
tau.beta ~ dgamma(0.01,0.01)
}
Inits (Run 1) list(alpha0=5, beta0=-1, tau.alpha=2, tau.beta=0.5, tau=1 )
Inits (Run 2) list(alpha0=20, beta0=-5, tau.alpha=20, tau.beta=5, tau=0.1 )
Inits (Run 3) list(alpha0=-10, beta0=5, tau.alpha=0.2, tau.beta=0.05, tau=10 )
Best regards,
Chin
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