cernstaff.C: Playing with a Tree containing variables of type character

// Playing with a Tree containing variables of type character
// Author: Rene Brun
void cernstaff () {
   TString dir = gSystem->DirName(__FILE__);
   if (gSystem->AccessPathName(dir+"/cernstaff.root")) {
      gROOT->SetMacroPath(dir);
      gROOT->ProcessLine(".x cernbuild.C");
   }
   TFile *f = new TFile(dir+"/cernstaff.root");
   TTree *T = (TTree*)f->Get("T");
   TCanvas *c1 = new TCanvas("c1","CERN staff",10,10,1000,750);
   c1->SetFillColor(17);
   c1->Divide(2,2);
   // make table of number of people per Nation & Division
   c1->cd(1); gPad->SetGrid();
   T->Draw("Nation:Division>>hN","","text");
   TH2F *hN = (TH2F*)gDirectory->Get("hN");
   hN->SetMarkerSize(1.6);
   hN->SetStats(0);
   
   //make profile of Average cost per Nation
   c1->cd(2); gPad->SetGrid();
   gPad->SetLeftMargin(0.12);
   T->Draw("Cost:Nation>>hNation","","prof,goff");
   TH1F *hNation = (TH1F*)gDirectory->Get("hNation");
   hNation->SetTitle("Average Cost per Nation");
   hNation->LabelsOption(">"); //sort by decreasing bin contents
   hNation->SetMaximum(13000);
   hNation->SetMinimum(7000);
   hNation->SetStats(0);
   hNation->SetMarkerStyle(21);
   hNation->Draw();
   
   //make stacked plot of Nations versus Grade
   c1->cd(3); gPad->SetGrid();
   THStack *hGrades = new THStack("hGrades","Nations versus Grade");
   TH1F *hFR = new TH1F("hFR","FR",12,3,15);
    hFR->SetFillColor(kCyan);
    hGrades->Add(hFR);
    T->Draw("Grade>>hFR","Nation==\"FR\"");
   TH1F *hCH = new TH1F("hCH","CH",12,3,15);
    hCH->SetFillColor(kRed);
    hGrades->Add(hCH);
    T->Draw("Grade>>hCH","Nation==\"CH\"");
   TH1F *hIT = new TH1F("hIT","IT",12,3,15);
    hIT->SetFillColor(kGreen);
    hGrades->Add(hIT);
    T->Draw("Grade>>hIT","Nation==\"IT\"");
   TH1F *hDE = new TH1F("hDE","DE",12,3,15);
    hDE->SetFillColor(kYellow);
    hGrades->Add(hDE);
    T->Draw("Grade>>hDE","Nation==\"DE\"");
   TH1F *hGB = new TH1F("hGB","GB",12,3,15);
    hGB->SetFillColor(kBlue);
    hGrades->Add(hGB);
    T->Draw("Grade>>hGB","Nation==\"GB\"");
   hGrades->Draw();
   TLegend *legend = new TLegend(0.7,0.65,0.86,0.88);
   legend->AddEntry(hGB,"GB","f");
   legend->AddEntry(hDE,"DE","f");
   legend->AddEntry(hIT,"IT","f");
   legend->AddEntry(hCH,"CH","f");
   legend->AddEntry(hFR,"FR","f");
   legend->Draw();
   
   //make histogram of age distribution
   c1->cd(4); gPad->SetGrid();
   T->Draw("Age");
   T->Draw("Age>>hRetired","Age>(65-2002+1988)","same");
   TH1F *hRetired = (TH1F*)gDirectory->Get("hRetired");
   hRetired->SetFillColor(kRed);
   hRetired->SetFillStyle(3010);
   
   TArrow *arrow = new TArrow(32,169,55,74,0.03,"|>");
   arrow->SetFillColor(1);
   arrow->SetFillStyle(1001);
   arrow->Draw();
   
   TPaveText *pt = new TPaveText(0.12,0.8,0.55,0.88,"brNDC");
   pt->SetFillColor(18);
   pt->AddText("People at CERN in 1988");
   pt->AddText("and retired in 2002");
   pt->Draw();
   
   c1->cd(); 
}