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Reference Guide
jets.C File Reference

Detailed Description

Usage of a Tree using the JetEvent class.

The JetEvent class has several collections (TClonesArray) and other collections (TRefArray) referencing objects in the TClonesArrays. The JetEvent class is in $ROOTSYS/tutorials/tree/JetEvent.h,cxx to execute the script, do

.x jets.C
void jets()
Definition: jets.C:38
#include "TFile.h"
#include "TTree.h"
#include "TRandom.h"
#include "TROOT.h"
#include "TSystem.h"
#include "JetEvent.h"
#include "Riostream.h"
void write(Int_t nev=100) {
//write nev Jet events
TFile f("JetEvent.root","recreate");
TTree *T = new TTree("T","Event example with Jets");
JetEvent *event = new JetEvent;
for (Int_t ev=0;ev<nev;ev++) {
void read() {
//read the JetEvent file
TFile f("JetEvent.root");
TTree *T = (TTree*)f.Get("T");
JetEvent *event = 0;
T->SetBranchAddress("event", &event);
Long64_t nentries = T->GetEntries();
for (Long64_t ev=0;ev<nentries;ev++) {
if (ev) continue; //dump first event only
cout << " Event: "<< ev
<< " Jets: " << event->GetNjet()
<< " Tracks: " << event->GetNtrack()
<< " Hits A: " << event->GetNhitA()
<< " Hits B: " << event->GetNhitB() << endl;
void pileup(Int_t nev=200) {
//make nev pileup events, each build with LOOPMAX events selected
//randomly among the nentries
TFile f("JetEvent.root");
TTree *T = (TTree*)f.Get("T");
// Long64_t nentries = T->GetEntries();
const Int_t LOOPMAX=10;
JetEvent *events[LOOPMAX];
Int_t loop;
for (loop=0;loop<LOOPMAX;loop++) events[loop] = 0;
for (Long64_t ev=0;ev<nev;ev++) {
if (ev%10 == 0) printf("building pileup: %lld\n",ev);
for (loop=0;loop<LOOPMAX;loop++) {
Int_t rev = gRandom->Uniform(LOOPMAX);
T->SetBranchAddress("event", &events[loop]);
void jets(Int_t nev=100, Int_t npileup=200, Bool_t secondrun = true) {
// Embedding these loads inside the first run of the script is not yet
// supported in v6
// gROOT->ProcessLine(".L $ROOTSYS/tutorials/tree/JetEvent.cxx+");
//void jets(Int_t nev=100, Int_t npileup=200, Bool_t secondrun);
void jets(Int_t nev=100, Int_t npileup=200) {
TString tutdir = gROOT->GetTutorialDir();
gROOT->ProcessLine(".L " + tutdir + "/tree/JetEvent.cxx+");
gROOT->ProcessLine("#define JETS_SECOND_RUN yes");
gROOT->ProcessLine("#include \"" __FILE__ "\"");
#define f(i)
Definition: RSha256.hxx:104
bool Bool_t
Definition: RtypesCore.h:63
int Int_t
Definition: RtypesCore.h:45
long long Long64_t
Definition: RtypesCore.h:80
int nentries
Definition: THbookFile.cxx:91
#define gROOT
Definition: TROOT.h:404
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition: TFile.h:54
virtual Double_t Uniform(Double_t x1=1)
Returns a uniform deviate on the interval (0, x1).
Definition: TRandom.cxx:672
Basic string class.
Definition: TString.h:136
A TTree represents a columnar dataset.
Definition: TTree.h:79
double T(double x)
Definition: ChebyshevPol.h:34
Rene Brun

Definition in file jets.C.