model {
  for(i in 1:N) {                          
        is.censored[i] ~ dinterval(t[i], last.t[i]);
        t[i] ~ dweib(r,mu[i]);  
                                           
        mu[i] <- exp(beta[group[i]]);      # relative risk model
  }
  for(j in 1:M) {
        beta[j] ~ dnorm(0.0, 0.0001);      # prior
        median[j] <- pow(log(2) *          # median survival
                       exp(-beta[j]), 1/r);  
  }
  r ~ dgamma(1.0,0.0001);      # slowly decreasing on +ve reals

  irr.control <- beta[1];                  # change 
  veh.control <- beta[2]-beta[1];          # parameterisation           
  test.sub <- beta[3]-beta[1];
  pos.control <- beta[4]-beta[1];
}