hsimple.C File Reference

Detailed Description

This program creates :

• a one dimensional histogram
• a two dimensional histogram
• a profile histogram
• a memory-resident ntuple

These objects are filled with some random numbers and saved on a file. If get=1 the macro returns a pointer to the TFile of "hsimple.root" if this file exists, otherwise it is created. The file "hsimple.root" is created in $ROOTSYS/tutorials if the caller has write access to this directory, otherwise the file is created in $PWD

(TFile *) 0x55704eaeb0a0

 
#include <TFile.h>
#include <TNtuple.h>
#include <TH2.h>
#include <TProfile.h>
#include <TCanvas.h>
#include <TFrame.h>
#include <TROOT.h>
#include <TSystem.h>
#include <TRandom3.h>
#include <TBenchmark.h>
#include <TInterpreter.h>
 
TFile *hsimple(Int_t getFile=0)
{
   TString filename = "hsimple.root";
   TString dir = gROOT->GetTutorialDir();
   dir.ReplaceAll("/./","/");
   TFile *hfile = nullptr;
   if (getFile) {
      // if the argument getFile =1 return the file "hsimple.root"
      // if the file does not exist, it is created
      TString fullPath = dir+"hsimple.root";
      if (!gSystem->AccessPathName(fullPath,kFileExists)) {
         hfile = TFile::Open(fullPath); //in $ROOTSYS/tutorials
         if (hfile) return hfile;
      }
      //otherwise try $PWD/hsimple.root
      if (!gSystem->AccessPathName("hsimple.root",kFileExists)) {
         hfile = TFile::Open("hsimple.root"); //in current dir
         if (hfile) return hfile;
      }
   }
   //no hsimple.root file found. Must generate it !
   //generate hsimple.root in current directory if we have write access
   if (gSystem->AccessPathName(".",kWritePermission)) {
      printf("you must run the script in a directory with write access\n");
      return nullptr;
   }
   hfile = (TFile*)gROOT->FindObject(filename); if (hfile) hfile->Close();
   hfile = new TFile(filename,"RECREATE","Demo ROOT file with histograms");
 
   // Create some histograms, a profile histogram and an ntuple, add them to hfile
   TH1F *hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
   hpx->SetDirectory(hfile);
   hpx->SetFillColor(48);
   TH2F *hpxpy = new TH2F("hpxpy","py vs px",40,-4,4,40,-4,4);
   hpxpy->SetDirectory(hfile);
   TProfile *hprof = new TProfile("hprof","Profile of pz versus px",100,-4,4,0,20);
   hprof->SetDirectory(hfile);
   TNtuple *ntuple = new TNtuple("ntuple","Demo ntuple","px:py:pz:random:i");
 
   // Set to "true" if you want to see in the output how much time it took to fill the histogram:
   const bool doBenchmark = false;
 
   if (doBenchmark)
      gBenchmark->Start("hsimple");
 
   // Create a new canvas.
   TCanvas *c1 = new TCanvas("c1","Dynamic Filling Example",200,10,700,500);
   c1->SetFillColor(42);
   c1->GetFrame()->SetFillColor(21);
   c1->GetFrame()->SetBorderSize(6);
   c1->GetFrame()->SetBorderMode(-1);
 
 
   // Fill histograms randomly
   TRandom3 randomNum;
   Float_t px, py, pz;
   const Int_t kUPDATE = 1000;
   for (Int_t i = 0; i < 25000; i++) {
      randomNum.Rannor(px,py);
      pz = px*px + py*py;
      Float_t rnd = randomNum.Rndm();
      hpx->Fill(px);
      hpxpy->Fill(px,py);
      hprof->Fill(px,pz);
      ntuple->Fill(px,py,pz,rnd,i);
      if (i && (i%kUPDATE) == 0) {
         if (i == kUPDATE) hpx->Draw();
         c1->Modified();
         c1->Update();
         if (gSystem->ProcessEvents())
            break;
      }
   }
   if (doBenchmark)
      gBenchmark->Show("hsimple");
 
   // Save all objects in this file
   hpx->SetFillColor(0);
   hfile->Write();
   hpx->SetFillColor(48);
   c1->Modified();
   return hfile;
 
   // Note that the file is automatically close when application terminates
   // or when the file destructor is called.
}

Author

Rene Brun

Definition in file hsimple.C.