Plot 3D Histogram from hit positions

[Yasir_Ali]

Dear Experts

I need some help in plotting 3D Grid (Histogram) for the hit positions given in root file in Tree. I am not sure if this code will work.

#include "TGraphErrors.h"
#include "TF1.h"
#include "TF2.h"
#include "TF3.h"
#include "TRandom.h"
#include "TCanvas.h"
#include "TLegend.h"
#include "TMath.h"

void draw_Performance(Int_t nevent=-1)
{

//==========Style of the plot============
   gStyle->SetPalette(1);
   gStyle->SetOptTitle(1);
   gStyle->SetTitleOffset(.85,"X");gStyle->SetTitleOffset(.85,"Y");
   gStyle->SetTitleSize(.04,"X");gStyle->SetTitleSize(.04,"Y");
   gStyle->SetLabelSize(.04,"X");gStyle->SetLabelSize(.04,"Y");
   gStyle->SetHistLineWidth(2);
   gStyle->SetOptFit(1);
   gStyle->SetOptStat(0);
     
//=======Reading the root file DD4HEP===========

   TFile* file = new TFile("eicrecon.root"); // Tree with tracks and hits
		
		// Create the tree reader and its data containers
   
   TTree *t = (TTree*)file->Get("myFirstPlugin/tree_Hits");
 
   t->Branch ("E" , &E);
   t->Branch ("x" , &x);
   t->Branch ("y",  &y);
   t->Branch ("r",  &r);
 
    const int ngraph = 1; 
 TCanvas * c[ngraph]; 
 for (int i =0; i<ngraph; ++i){
 c[i] = new TCanvas(Form("c%d",i),Form("c%d",i),1200,1000);
 c[i]->SetMargin(0.09, 0.1 ,0.1,0.06);
  }
 
   TH3F *hit = new TH3F("hit", "hit_dist",2500,0 ,50, 2500,0 ,50, 2500,0 ,50);
   //TH1F *tot_energy = new TH1F("tot_energy", "edep", 500, 0, 100);
   
 	hit->GetXaxis()->SetTitle("hit_distribution");
 	hit->GetXaxis()->CenterTitle();
 
     
     for (int i=0; i<t->GetEntries(); i++)
 	{
 	t->GetEntry (i);

         hit->Fill(i); // need to plot 3D
      }
     
     c[0]->cd();
     hit->Draw();
     c[0]->SaveAs("hit_distribution.png");
     
}

[bellenot]

Welcome to the ROOT Forum!

@Yasir_Ali

I am not sure if this code will work.

I would say that the best way to know is to try

[Wile_E_Coyote]

Try:

void draw_Performance(Long64_t nevents = TTree::kMaxEntries) {
  TFile *f = TFile::Open("eicrecon.root");
  if ((!f) || f->IsZombie()) { delete f; return; } // just a precaution
  TTree *t; f->GetObject("myFirstPlugin/tree_Hits", t);
  if (!t) { delete f; return; } // just a precaution
  // t->Print();
  gROOT->cd(); // newly created histograms should go here
  TH3F *h = new TH3F("hits", "E;x;y;r", 250, 0., 50., 250, 0., 50., 250, 0., 50.);
  t->Project("hits", "r:y:x", "E", "", nevents);
  h->Draw("box2");
  delete f; //automatically deletes t, too
}

[Yasir_Ali]

Thanks Wile Actually in this root file x y and z positions are at 0 This 3D looks like

[Wile_E_Coyote]

Try with “automatic bins”, e.g.:
TH3F *h = new TH3F("hits", "E;x;y;r", 100, 0., 0., 100, 0., 0., 100, 0., 0.);