hbars.C: Example of bar charts with 1-d histograms

// Example of bar charts with 1-d histograms
// Author: Rene Brun
void hbars() {
   cout << gSystem->DirName(gInterpreter->GetCurrentMacroName()) << endl;
   // try to open first the file cernstaff.root in tutorials/tree directory
   TString filedir = gSystem->DirName(gInterpreter->GetCurrentMacroName());
   filedir += TString("/../tree/");
   TString filename = filedir + "cernstaff.root";
   bool fileNotFound = gSystem->AccessPathName(filename); // note opposite return code
   // if file is not found try to generate it uing the macro tree/cernbuild.C
   if (fileNotFound) {
      TString macroName = filedir + "cernbuild.C";
      if (!gInterpreter->IsLoaded(macroName)) gInterpreter->LoadMacro(macroName);
      gROOT->ProcessLineFast("cernbuild()");
   }
   TFile * f = TFile::Open(filename);
   if (!f) {
      Error("hbars","file cernstaff.root not found");
      return; 
   }
   TTree *T = (TTree*)f->Get("T");
   if (!T) { 
      Error("hbars","Tree T is not present in file %s",f->GetName() );
      return;
   }
   T->SetFillColor(45);
   TCanvas *c1 = new TCanvas("c1","histograms with bars",700,800);
   c1->SetFillColor(42);
   c1->Divide(1,2);
   
   //horizontal bar chart
   c1->cd(1); gPad->SetGrid(); gPad->SetLogx(); gPad->SetFrameFillColor(33);
   T->Draw("Nation","","hbar2");
   
   //vertical bar chart
   c1->cd(2); gPad->SetGrid(); gPad->SetFrameFillColor(33);
   T->Draw("Division>>hDiv","","goff");
   TH1F *hDiv   = (TH1F*)gDirectory->Get("hDiv");
   hDiv->SetStats(0);
   TH1F *hDivFR = (TH1F*)hDiv->Clone("hDivFR");
   T->Draw("Division>>hDivFR","Nation==\"FR\"","goff");
   hDiv->SetBarWidth(0.45);
   hDiv->SetBarOffset(0.1);
   hDiv->SetFillColor(49);
   TH1 *h1 = hDiv->DrawCopy("bar2");
   hDivFR->SetBarWidth(0.4);
   hDivFR->SetBarOffset(0.55);
   hDivFR->SetFillColor(50);
   TH1 *h2 = hDivFR->DrawCopy("bar2,same");
  
   TLegend *legend = new TLegend(0.55,0.65,0.76,0.82);
   legend->AddEntry(h1,"All nations","f");
   legend->AddEntry(h2,"French only","f");
   legend->Draw();
   
   c1->cd();
   delete f;
}