void testTHStack() {
  TCanvas *c1 = new TCanvas("c1","stacked hists", 600, 900);
  c1->Divide(1,3);

  THStack hs("hs","test stacked histograms");
  TH1F *h1 = new TH1F("h1","test hstack",100,-4,4);
  h1->FillRandom("gaus",20000);
  h1->SetFillColor(kRed);
  hs.Add(h1);
  TH1F *h2 = new TH1F("h2","test hstack",100,-4,4);
  h2->FillRandom("gaus",15000);
  h2->SetFillColor(kBlue);
  hs.Add(h2);
  TH1F *h3 = new TH1F("h3","test hstack",100,-4,4);
  h3->FillRandom("gaus",10000);
  h3->SetFillColor(kGreen);
  hs.Add(h3);

  c1->cd(1);
  hs.Draw("A");

  c1->cd(2);
  hs.Draw("nostack");

  c1->cd(3);
  TH1F * myhist = (TH1F*)hs.GetHistogram();
  myhist->Draw();
}