model {
  for (i in 1:n) {
     predcones[i] <- exp(a[grp[i]]+b[grp[i]]*DBH[i])
     gammarate[i] <- k/predcones[i]
     prob[i] ~ dgamma(k,gammarate[i])
     cones[i] ~ dpois(prob[i])
  }
a[1] ~ dnorm(0,0.01)
a[2] ~ dnorm(0,0.01)
b[1] ~ dnorm(0,0.01)
b[2] ~ dnorm(0,0.01)
k ~ dunif(0.1,5)
}