doc/v606/hbars_8C.html

TCanvas *hbars() {

   cout << gSystem->DirName(__FILE__) << endl;


   // Try to open first the file cernstaff.root in tutorials/tree directory

   TString filedir = gSystem->DirName(__FILE__);

   filedir += TString("/../tree/");

   TString filename = "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 0;

   }

   TTree *T = (TTree*)f->Get("T");

   if (!T) {

      Error("hbars","Tree T is not present in file %s",f->GetName() );

      return 0;

   }

   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;

   return c1;

}