doc/v606/hsimpleReader_8C.html

#include "TFile.h"

#include "TH1F.h"

#include "TTreeReader.h"

#include "TTreeReaderValue.h"


void hsimpleReader() {

   // Create a histogram for the values we read.

   auto myHist = new TH1F("h1","ntuple",100,-4,4);


   // Open the file containing the tree.

   auto myFile = TFile::Open("hsimple.root");

   if (!myFile || myFile->IsZombie()) {

      return;

   }

   // Create a TTreeReader for the tree, for instance by passing the

   // TTree's name and the TDirectory / TFile it is in.

   TTreeReader myReader("ntuple", myFile);


   // The branch "px" contains floats; access them as myPx.

   TTreeReaderValue<Float_t> myPx(myReader, "px");

   // The branch "py" contains floats, too; access those as myPy.

   TTreeReaderValue<Float_t> myPy(myReader, "py");


   // Loop over all entries of the TTree or TChain.

   while (myReader.Next()) {

      // Just access the data as if myPx and myPy were iterators (note the '*'

      // in front of them):

      myHist->Fill(*myPx + *myPy);

   }


   myHist->Draw();

}