TNtuple do not work

ROOT
1

Hallo everybody,

I have the following problem. I want to use TNtuple, and for that I made the following program to test it:

#include <iostream>
#include <TTree.h>
#include <TNtuple.h>
#include <TFile.h>

using namespace std;

int main(int argc, char **argv) {
  
  TFile * outPut = new TFile("outPut.root","RECREATE"); 
  TNtuple * myTree = new TNtuple("meins", "", "a:b:c:d");

   myTree->Fill(1,2,3,4);
   myTree->Fill(1,2,5,6);
   myTree->Fill(1,2,7,8);
   myTree->Fill(1,2,9,10);
       
    outPut->Write();
    outPut->Close();
  
  }
}

the compiling works without any error, but if I try to start the program, there come the error:

Warning in <TFile::Write>: file outPut.root not opened in write mode
Warning in <TFile::Write>: file outPut.root not opened in write mode

 *** Break *** segmentation violation

what is my mistake?

cheers
Prometheus

2

Hi,

I can not reproduce this problem. One possibility is that you current (OS) directory is not writeable.

CHeers,
Philippe.

3

Hi Philippe,

thank you, you were right :slight_smile:

but now, I have the next problem: if I try to use the TNtuple in root like that:

root [0] TFile *_file0=TFile::Open("outPut.root")
root [1] TH2D* tmp = new TH2D("tmp","",100,0,100,100,0,100)
root [2] myTree->Project("tmp","a:b","")

I get this error:

Error: Symbol myTree is not defined in current scope  (tmpfile):1:
Error: Failed to evaluate myTree->Project("tmp","a:b","")
*** Interpreter error recovered ***

where is my mistake?

cheers
Prometheus

4

Hi,

Unless you ntuple was named ‘myTree’ (in which case CINT would have done the load of the object for you) you are missing the reading the ntuple:root [0] TFile *_file0=TFile::Open("outPut.root") root [1] TTree*myTree = 0; _file0->GetObject("meins",myTree); root [2] TH2D* tmp = new TH2D("tmp","",100,0,100,100,0,100) root [3] myTree->Project("tmp","a:b","")

Cheers,
Philippe.

5

yes, now it works :slight_smile:

thank you a lot of!