test_fit() {

  gROOT->SetStyle("Plain");

  gStyle->SetOptFit(1111);
  
  TFile * file = new TFile("test_fit.root");
  TH1F * h = (TH1F*) file->Get("h");
  TF1 * f = new TF1("f", "[0] * TMath::Gaus(x, [1], [2])", 0, 100);
  f->SetParameters(0.6, 60, 20);
  h->Fit(f, "", "", 0, 100);
  
}