# varying-intercept, varying-slope radon model for earnings by ethnicity
# modeling the correlation

model {
  for (i in 1:n){
    y[i] ~ dnorm (y.hat[i], tau.y)
    y.hat[i] <- a[eth[i]] + b[eth[i]]*x[i]
  }
  tau.y <- pow(sigma.y, -2)
  sigma.y ~ dunif (0, 100)

  for (j in 1:n.eth){
    a[j] <- B[j,1]
    b[j] <- B[j,2]
    B[j,1:2] ~ dmnorm (B.hat[j,], Tau.B[,])
    B.hat[j,1] <- mu.a
    B.hat[j,2] <- mu.b
  }
  mu.a~ dnorm (0, .0001)
  mu.b ~ dnorm (0, .0001)

  Tau.B[1:2,1:2] <- inverse(Sigma.B[,])
  Sigma.B[1,1] <- pow(sigma.a, 2)
  sigma.a ~ dunif (0, 100)
  Sigma.B[2,2] <- pow(sigma.b, 2)
  sigma.b ~ dunif (0, 100)
  Sigma.B[1,2] <- rho*sigma.a*sigma.b
  Sigma.B[2,1] <- Sigma.B[1,2]
  rho ~ dunif (-1, 1)
}