sample_beta

// [[Rcpp::export]]
NumericMatrix sample_tau_pg(NumericMatrix beta,
                            double a_beta, double b_beta) {
  int P = beta.nrow();
  int G = beta.ncol();
  
  NumericMatrix tau_pg(P, G);
  
  for(int p = 0; p < P; p++) {
    for(int g = 0; g < G; g++) {
      double beta_new = b_beta + beta(p,g) * beta(p,g) / 2;
      tau_pg(p,g) = as<double>(rgamma(1, a_beta + 1, 1 / beta_new));
    }
  }
  return tau_pg;
}