model headway

{p0[1]<-0.5
 p0[2]<-0.5
 cc[1]~dcat(p0[])
 for (i in 2:30) 
     {cc[i]~dcat(q[,cc[i-1]])   # This is the "burn-in" section.
      }
 
 c[1]~dcat(q[,cc[30]])
 t[1]~dgamma(alpha[c[1]],beta[c[1]])


 for (i in 2:N) 
     {c[i]~dcat(q[,c[i-1]])
      t[i]~dgamma(alpha[c[i]],beta[c[i]])
      }
 
 alpha[1]<-1
 alpha[2]<-1+aa
 aa~dgamma(1,0.5)
 beta[1]~dgamma(2,8) I(,bb)
 beta[2]<-alpha[2]*bb
 bb~dgamma(1,2) I(beta[1],)
 pi[1]~dbeta(1,2)
 pi[2]~dbeta(1,2)
 q[1,1]<-pi[1]
 q[1,2]<-pi[2]
 q[2,1]<-1-pi[1]
 q[2,2]<-1-pi[2]

 lrr<-log(pi[1]/pi[2])
 pos<-step(lrr)
 mu[1]<-1/beta[1]
 mu[2]<-1/bb
}