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.
Author: Rene Brun
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Wednesday, April 17, 2024 at 11:23 AM.
Definition of a helper function:
%%cpp -d
#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();
}
Definition of a helper function:
%%cpp -d
void tree3r()
{
TFile *f = new TFile("tree3.root");
TTree *t3 = (TTree*)f->Get("t3");
t3->AddFriend("t3f","tree3f.root");
t3->Draw("pz","pt>3");
}
Definition of a helper function:
%%cpp -d
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");
}
tree3w();
tree3r();
tree3r2();
****************************************************************************** *Tree :t3 : Reconst ntuple * *Entries : 1000 : Total = 7018766 bytes File Size = 4403660 * * : : Tree compression factor = 1.55 * ****************************************************************************** *Br 0 :ntrack : ntrack/I * *Entries : 1000 : Total Size= 4647 bytes One basket in memory * *Baskets : 0 : Basket Size= 32000 bytes Compression= 1.00 * *............................................................................* *Br 1 :stat : stat[ntrack]/I * *Entries : 1000 : Total Size= 1002090 bytes File Size = 16050 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 60.65 * *............................................................................* *Br 2 :sign : sign[ntrack]/I * *Entries : 1000 : Total Size= 1002090 bytes File Size = 16427 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 59.25 * *............................................................................* *Br 3 :px : px[ntrack]/F * *Entries : 1000 : Total Size= 1002023 bytes File Size = 903860 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 1.08 * *............................................................................* *Br 4 :py : py[ntrack]/F * *Entries : 1000 : Total Size= 1002023 bytes File Size = 906967 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 1.07 * *............................................................................* *Br 5 :pz : pz[ntrack]/F * *Entries : 1000 : Total Size= 1002023 bytes File Size = 870601 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 1.12 * *............................................................................* *Br 6 :zv : zv[ntrack]/F * *Entries : 1000 : Total Size= 1002023 bytes File Size = 784206 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 1.24 * *............................................................................* *Br 7 :chi2 : chi2[ntrack]/F * *Entries : 1000 : Total Size= 1002097 bytes File Size = 905549 * *Baskets : 31 : Basket Size= 32000 bytes Compression= 1.07 * *............................................................................*
Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
Draw all canvases
gROOT->GetListOfCanvases()->Draw()