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tree3.C File Reference

Detailed Description

View in nbviewer Open in SWAN Example of a Tree where branches are variable length arrays A second Tree is created and filled in parallel. Run this script with

.x tree3.C

In the function treer, the first Tree is open. The second Tree is declared friend of the first tree. TTree::Draw is called with variables from both Trees.

#include "TFile.h"
#include "TTree.h"
#include "TRandom.h"
#include "TCanvas.h"
void tree3w() {
const Int_t kMaxTrack = 500;
Int_t ntrack;
Int_t stat[kMaxTrack];
Int_t sign[kMaxTrack];
Float_t px[kMaxTrack];
Float_t py[kMaxTrack];
Float_t pz[kMaxTrack];
Float_t pt[kMaxTrack];
Float_t zv[kMaxTrack];
Float_t chi2[kMaxTrack];
Double_t sumstat;
TFile f("tree3.root","recreate");
TTree *t3 = new TTree("t3","Reconst ntuple");
t3->Branch("ntrack",&ntrack,"ntrack/I");
t3->Branch("stat",stat,"stat[ntrack]/I");
t3->Branch("sign",sign,"sign[ntrack]/I");
t3->Branch("px",px,"px[ntrack]/F");
t3->Branch("py",py,"py[ntrack]/F");
t3->Branch("pz",pz,"pz[ntrack]/F");
t3->Branch("zv",zv,"zv[ntrack]/F");
t3->Branch("chi2",chi2,"chi2[ntrack]/F");
TFile fr("tree3f.root","recreate");
TTree *t3f = new TTree("t3f","a friend Tree");
t3f->Branch("ntrack",&ntrack,"ntrack/I");
t3f->Branch("sumstat",&sumstat,"sumstat/D");
t3f->Branch("pt",pt,"pt[ntrack]/F");
for (Int_t i=0;i<1000;i++) {
Int_t nt = gRandom->Rndm()*(kMaxTrack-1);
ntrack = nt;
sumstat = 0;
for (Int_t n=0;n<nt;n++) {
stat[n] = n%3;
sign[n] = i%2;
px[n] = gRandom->Gaus(0,1);
py[n] = gRandom->Gaus(0,2);
pz[n] = gRandom->Gaus(10,5);
zv[n] = gRandom->Gaus(100,2);
chi2[n] = gRandom->Gaus(0,.01);
sumstat += chi2[n];
pt[n] = TMath::Sqrt(px[n]*px[n] + py[n]*py[n]);
}
t3->Fill();
t3f->Fill();
}
t3->Print();
f.cd();
t3->Write();
fr.cd();
t3f->Write();
}
void tree3r()
{
TFile *f = new TFile("tree3.root");
TTree *t3 = (TTree*)f->Get("t3");
t3->AddFriend("t3f","tree3f.root");
t3->Draw("pz","pt>3");
}
void tree3r2()
{
TPad *p = new TPad("p","p",0.6, 0.4, 0.98, 0.8);
p->Draw(); p->cd();
TFile *f1 = new TFile("tree3.root");
TFile *f2 = new TFile("tree3f.root");
TTree *t3 = (TTree*)f1->Get("t3");
t3->AddFriend("t3f",f2);
t3->Draw("pz","pt>3");
}
void tree3()
{
tree3w();
tree3r();
tree3r2();
}
Author
Rene Brun

Definition in file tree3.C.

n
const Int_t n
Definition: legend1.C:16
TRandom::Gaus
virtual Double_t Gaus(Double_t mean=0, Double_t sigma=1)
Samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigm...
Definition: TRandom.cxx:263
f
#define f(i)
Definition: RSha256.hxx:122
TPad
Definition: TPad.h:26
TTree
Definition: TTree.h:79
TMath::Sqrt
Double_t Sqrt(Double_t x)
Definition: TMath.h:691
TRandom.h
Float_t
float Float_t
Definition: RtypesCore.h:57
Int_t
int Int_t
Definition: RtypesCore.h:45
TTree::Print
virtual void Print(Option_t *option="") const
Print a summary of the tree contents.
Definition: TTree.cxx:7090
TTree::Fill
virtual Int_t Fill()
Fill all branches.
Definition: TTree.cxx:4527
TCanvas.h
TTree.h
TFile.h
TTree::Write
virtual Int_t Write(const char *name=0, Int_t option=0, Int_t bufsize=0)
Write this object to the current directory.
Definition: TTree.cxx:9563
TTree::AddFriend
virtual TFriendElement * AddFriend(const char *treename, const char *filename="")
Add a TFriendElement to the list of friends.
Definition: TTree.cxx:1310
TTree::Branch
TBranch * Branch(const char *name, T *obj, Int_t bufsize=32000, Int_t splitlevel=99)
Add a new branch, and infer the data type from the type of obj being passed.
Definition: TTree.h:349
gRandom
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
TTree::Draw
virtual void Draw(Option_t *opt)
Default Draw method for all objects.
Definition: TTree.h:427
TRandom::Rndm
virtual Double_t Rndm()
Machine independent random number generator.
Definition: TRandom.cxx:541
TFile
Definition: TFile.h:54
f1
TF1 * f1
Definition: legend1.C:11
Double_t
double Double_t
Definition: RtypesCore.h:59
TPad::cd
TVirtualPad * cd(Int_t subpadnumber=0)
Set Current pad.
Definition: TPad.cxx:594
pt
TPaveText * pt
Definition: entrylist_figure1.C:7
TPad::Draw
virtual void Draw(Option_t *option="")
Draw Pad in Current pad (re-parent pad if necessary).
Definition: TPad.cxx:1285