TCanvas *hstack_macro() {
// Example of stacked histograms: class THStack
//
//  Author: Rene Brun

   gROOT->Reset();

   // TStyle* thisStyle = new TStyle("ThisStyle", "ThisStyle");
   // thisStyle->SetFillColor(kRed);
   // thisStyle->SetMarkerStyle(21);
   // thisStyle->SetMarkerColor(kRed);
   // thisStyle->cd();

   // Open WZ
   TFile *f_wz = new TFile("wz_sm_resonance_v3_all.root");
   // f_wz->ls();
   // f_wz->ShowStreamerInfo();

   // ttbar
   TFile *f_ttbar = new TFile("ttbar_resonance_v3_all.root");
   
   // zgamma
   TFile *f_zgamma = new TFile("zgamma_resonance_v3_all.root");
   
   // zpjets
   TFile *f_zpjets = new TFile("zpjets_resonance_v3_all.root");
   
   // zz
   TFile *f_zz = new TFile("zz_resonance_v3_all.root");


   THStack *hs = new THStack("hs","Stacked 1D histograms");


   TH1F *h1_wz = (TH1F*) f_wz->Get("h_mwz");
   h1_wz->SetFillColor(kYellow);
   h1_wz->SetLineColor(kYellow);
   h1_wz->SetMarkerStyle(0);
   h1_wz->SetMarkerColor(kYellow);
   hs->Add(h1_wz);

   TH1F *h1_zgamma = (TH1F*) f_zgamma->Get("h_mwz");
   h1_zgamma->SetFillColor(kCyan);
   h1_zgamma->SetLineColor(kCyan);
   h1_zgamma->SetMarkerStyle(0);
   h1_zgamma->SetMarkerColor(kCyan);
   hs->Add(h1_zgamma);

   TH1F *h1_zpjets = (TH1F*) f_zpjets->Get("h_mwz");
   h1_zpjets->SetFillColor(kViolet);
   h1_zpjets->SetLineColor(kViolet);
   h1_zpjets->SetMarkerStyle(0);
   h1_zpjets->SetMarkerColor(kViolet);
   hs->Add(h1_zpjets);

   TH1F *h1_zz = (TH1F*) f_zz->Get("h_mwz");
   h1_zz->SetFillColor(kGreen);
   h1_zz->SetLineColor(kGreen);
   h1_zz->SetMarkerStyle(0);
   h1_zz->SetMarkerColor(kGreen);
   hs->Add(h1_zz);

   TCanvas *cst = new TCanvas("cst","stacked hists",10,10,700,700);
   cst->SetFillColor(0);
   hs->Draw("nostack,LF2"); 
   return cst;
}