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Reference Guide
hvector.C File Reference

Detailed Description

View in nbviewer Open in SWAN Write and read STL vectors in a tree.

pict1_hvector.C.png
#include <vector>
#include "TFile.h"
#include "TTree.h"
#include "TCanvas.h"
#include "TFrame.h"
#include "TH1F.h"
#include "TBenchmark.h"
#include "TRandom.h"
#include "TSystem.h"
void write()
{
TFile *f = TFile::Open("hvector.root","RECREATE");
if (!f) { return; }
// Create one histograms
TH1F *hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
hpx->SetFillColor(48);
std::vector<float> vpx;
std::vector<float> vpy;
std::vector<float> vpz;
std::vector<float> vrand;
// Create a TTree
TTree *t = new TTree("tvec","Tree with vectors");
t->Branch("vpx",&vpx);
t->Branch("vpy",&vpy);
t->Branch("vpz",&vpz);
t->Branch("vrand",&vrand);
// Create a new canvas.
TCanvas *c1 = new TCanvas("c1","Dynamic Filling Example",200,10,700,500);
const Int_t kUPDATE = 1000;
for (Int_t i = 0; i < 25000; i++) {
Int_t npx = (Int_t)(gRandom->Rndm(1)*15);
vpx.clear();
vpy.clear();
vpz.clear();
vrand.clear();
for (Int_t j = 0; j < npx; ++j) {
Float_t px,py,pz;
gRandom->Rannor(px,py);
pz = px*px + py*py;
Float_t random = gRandom->Rndm(1);
hpx->Fill(px);
vpx.emplace_back(px);
vpy.emplace_back(py);
vpz.emplace_back(pz);
vrand.emplace_back(random);
}
if (i && (i%kUPDATE) == 0) {
if (i == kUPDATE) hpx->Draw();
c1->Modified();
c1->Update();
break;
}
t->Fill();
}
f->Write();
delete f;
}
void read()
{
TFile *f = TFile::Open("hvector.root","READ");
if (!f) { return; }
TTree *t; f->GetObject("tvec",t);
std::vector<float> *vpx = 0;
// Create a new canvas.
TCanvas *c1 = new TCanvas("c1","Dynamic Filling Example",200,10,700,500);
const Int_t kUPDATE = 1000;
TBranch *bvpx = 0;
t->SetBranchAddress("vpx",&vpx,&bvpx);
// Create one histograms
TH1F *h = new TH1F("h","This is the px distribution",100,-4,4);
h->SetFillColor(48);
for (Int_t i = 0; i < 25000; i++) {
Long64_t tentry = t->LoadTree(i);
bvpx->GetEntry(tentry);
for (UInt_t j = 0; j < vpx->size(); ++j) {
h->Fill(vpx->at(j));
}
if (i && (i%kUPDATE) == 0) {
if (i == kUPDATE) h->Draw();
c1->Modified();
c1->Update();
break;
}
}
// Since we passed the address of a local variable we need
// to remove it.
}
void hvector()
{
gBenchmark->Start("hvector");
write();
read();
gBenchmark->Show("hvector");
}
Author
The ROOT Team

Definition in file hvector.C.