How to read an array with variable dimension from a tree?

ROOT
1

I have a “leaf” in the tree tau_N of int type, and array tau_a[tau_N] of floats. So the dimension of tau_a[tau_N] varies (in my case between 0 and 6). I’m tring to acces the values stored in tau_a[tau_N].

Example of what i tried:


#include <iostream>
#if !defined(__CINT__) || defined(__MAKECINT__)
#include <TFile.h>
#include <TTree.h>
#include <TH1F.h>
#include <TBranch.h>
#endif

TFile *f;
TTree *myTree;


Int_t t, N, A;
Int_t a[10];        //this can be the problem

void ReadFile(){
	f=TFile::Open("some_file.root");
}

void SumE(){
	myTree = (TTree*)f->Get("Cn/t1000");
	
	TBranch *Brt=myTree->GetBranch("tau_N");  // this works
	Brt->SetAddress(&t);
	
	TBranch *Bracc = myTree->GetBranch("tau_a");  // may be those two lines are wrong ?
	Bracc->SetAddress(a);
	
	N= myTree->GetEntries();
	
	for (Int_t i=0;i<N;i++) {
		myTree->GetEntry(i);
		A=0;
		for (int j=0;j<t;j++) {
			if (a[j]) {A++;}         // counting how many values of the array a are non zero
		}
		cout << A << " , " << endl;
	}

}

thanks for any help, asen.
PS: I’m not very skilled in C++ so pls. some simple solutions :smiley:

2

What you do should work. What is the problem?
Please post a small file to test your problem.

Rene

3

extracting the example form longer code I’ve chanded the names of some variables and actualy the vrong variable name was the problem. Instead of

Int_t a[10];

in my original code there was

Int_t accept[10];

OK, seems like accept is not the best name for a variable. :blush: