void barchart() {

  const int N=5;

  TH1F* h1 = new TH1F("barchart1", "error bars on bar chart", N, 0.5, N + 0.5);
  TH1F* h2 = new TH1F("barchart2", "barchart2", N, 0.5, N + 0.5);
  TH1F* h3 = new TH1F("barchart3", "barchart2", N, 0.5, N + 0.5);
  
  for (int i=1; i<=N; i++) {

    h1->SetBinContent(i, i-1.5);
    h2->SetBinContent(i, i-2.0);
    h3->SetBinContent(i, i-2.5);

    h1->SetBinError(i, 0.1);
    h2->SetBinError(i, 0.15);
    h3->SetBinError(i, 0.2);
  }

  h1->SetBarWidth(0.2);
  h2->SetBarWidth(0.2);
  h3->SetBarWidth(0.2);

  h1->SetBarOffset(0.2);
  h2->SetBarOffset(0.4);
  h3->SetBarOffset(0.6);

  h1->SetFillColor(2);
  h2->SetFillColor(3);
  h3->SetFillColor(4);

  h1->SetMaximum(N);
  h1->SetMinimum(-2.0);

  gStyle->SetCanvasColor(10); // white background
  gStyle->SetErrorX(0); // turn off horizontal error bars

  h1->Draw("bar2 e1");
  h2->Draw("bar2 e1 same");
  h3->Draw("bar2 e1 same");
}