double Bernstein(double* xArray, double* par){
  double x = xArray[0];
  double kd = par[0];
  double nd = par[1];
  int k = static_cast<int>(kd);
  int n = static_cast<int>(nd);
  double n_choose_k = TMath::Binomial(n,k);
  double b_kn = n_choose_k * pow(x,kd) * pow(1.-x, nd-kd);
  return b_kn;
}