Hi all, I want to study a large number of root files and I can't chain them. So I study files one by one. FOr somme coding reason, I need to apply a class inherited from a MakeClass() on each of the files. What I'm trying to do is : I open in the "update" mode, the file where I store the results of my studies. Then I declare (if it's the first time) or I "point at" the histograms and fill/update them. I use this in a C++ standalone mode. At the moment the file with the results is empty, and it seems that the histograms aren't detected. I coded it this way : //--- Check if histos exists TFile * f = TFile::Open("TriggStudies.root"); f->ls(); TH1F * check = NULL; check = (TH1F * ) f->Get("sJ_nev_mu"); cout << "check = " << check << endl; if (check == NULL) { //--- Histograms Creation cout << "| [#] Create Histograms for Trigger Studies" << endl; diJets_Nevts_mu = new TH1F("sJ_nev_mu","N evt vs Pt of Jet - L1 mu",75,0,150); } else { diJets_Nevts_mu = (TH1F * ) f->Get("sJ_nev_mu"); } the problem I have is that data files after data files, the "check" pointer is everytime empty. Does someone has an idea on what could be the source of this problem ? In an other way of saying that, Is it possible to fill histograms in a root file, close it, then reopen this file, update the histograms and re-close it again, and so on ... ? many thanks, take care, frederic. *---------------------------------------------------------* | Frederic Villeneuve-Seguier PHD - D0 experiment | | | | Centre de Physique des Particules de Marseille | | 163, avenue de Luminy 13288 | | Marseille Cedex 09 | | France | *---------------------------------------------------------* | Tel : 33 (0)4 91 82 76 13 | | Fax : 33 (0)4 91 82 72 99 | | e-mail: villeneuve@cppm.in2p3.fr | | homepage: http://marwww.in2p3.fr/~villeneu | *---------------------------------------------------------*
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