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hsimpleReader.C File Reference

Detailed Description

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TTreeReader simplest example.

Read data from hsimple.root (written by hsimple.C)

#include "TFile.h"
#include "TH1F.h"
#include "TTreeReader.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()) {
// 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);
static TFile * Open(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault, Int_t netopt=0)
Create / open a file.
Definition TFile.cxx:4082
1-D histogram with a float per channel (see TH1 documentation)
Definition TH1.h:621
An interface for reading values stored in ROOT columnar datasets.
A simple, robust and fast interface to read values from ROOT columnar datasets such as TTree,...
Definition TTreeReader.h:44
Anders Eie, 2013

Definition in file hsimpleReader.C.