[ROOT] Draw histogram from directory

From: Meta Binder (Meta.Binder@Physik.uni-muenchen.de)
Date: Wed Feb 19 2003 - 18:28:25 MET


Dear rooters,

I create a TFile with two subdirectories:
	TFile = histofile.root
	TDirectory subdirectories pythia, zjet

If I open the file in the TBrowser I can perfectly well access the 
histograms but I need to to this in a macro. I attached the histofile.root


my Macro:

#include <TH2.h>
#include <iostream>

TH1F *h;

int plot(){

  TFile *f = new TFile("histofile.root");
  
  pythia->cd();

  char hname[20];
  
  sprintf(hname,"h[%d]",0);
  h=(TH1F*)f->Get(hname);

  h->Draw();

}

gives
root [0]
Processing plot.C...
Error: illegal pointer to class object h 0x0 137  FILE:plot.C LINE:27
*** Interpreter error recovered ***


second problem:
-----------------------------------------------------------------------
if I do root histofile.root

root [0]
Attaching file histofile.root...
root [1] pythia->cd()
(Bool_t)1
root [2] gDirectory->pwd()
histofile.root:/pythia
root [3] gDirectory->cd()
(Bool_t)1
root [4] zjet->cd()
Error: Symbol zjet is not defined in current scope  
FILE:/tmp/fileihS306_cint LINE:1
Error: Failed to evaluate zjet->cd()Possible candidates are...
filename       line:size busy function type and name
*** Interpreter error recovered ***


But it is there. I can see it in the TBrowser.

What do I do wrong? 

Thank you so much.
Meta

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LMU Muenchen                 Meta Binder
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