Logo ROOT  
Reference Guide
 
Loading...
Searching...
No Matches
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();
}
#define f(i)
Definition RSha256.hxx:104
int Int_t
Definition RtypesCore.h:45
double Double_t
Definition RtypesCore.h:59
float Float_t
Definition RtypesCore.h:57
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
The most important graphics class in the ROOT system.
Definition TPad.h:26
TVirtualPad * cd(Int_t subpadnumber=0) override
Set Current pad.
Definition TPad.cxx:603
void Draw(Option_t *option="") override
Draw Pad in Current pad (re-parent pad if necessary).
Definition TPad.cxx:1299
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:274
virtual Double_t Rndm()
Machine independent random number generator.
Definition TRandom.cxx:552
A TTree represents a columnar dataset.
Definition TTree.h:79
virtual Int_t Fill()
Fill all branches.
Definition TTree.cxx:4590
virtual TFriendElement * AddFriend(const char *treename, const char *filename="")
Add a TFriendElement to the list of friends.
Definition TTree.cxx:1321
virtual void Print(Option_t *option="") const
Print a summary of the tree contents.
Definition TTree.cxx:7200
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:350
virtual void Draw(Option_t *opt)
Default Draw method for all objects.
Definition TTree.h:428
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:9686
TPaveText * pt
const Int_t n
Definition legend1.C:16
TF1 * f1
Definition legend1.C:11
Double_t Sqrt(Double_t x)
Definition TMath.h:691
Author
Rene Brun

Definition in file tree3.C.