Hi, I think this two features should be changed. 1; when creating a TNtuple object with only one variable it gives me error in filling time. It works fine with more variables. root [0] TNtuple *ntuple = new TNtuple("ntuple","Demo ntuple","px"); root [1] ntuple->Fill(1.); *** Break *** segmentation violation Root > 2; When drawing histogram from an empty TTree or TNtuple object directly to histogram, it doesn't fill nor create this histogram. I think it should create some default empty histogram, otherwise I get errors when trying to work with it. I tried to use empty trees, when there were not any particles passing detector in the simulation. Here is interpreter output and corresponding macro root [2] .x ttree-bug.C Error: No symbol histo in current scope FILE:ttree-bug.C LINE:12 Error: Failed to evaluate histo->SetTitle("my histo") FILE:ttree-bug.C LINE:12 Possible candidates are... filename line:size busy function type and name // macro demonstrating use of empty ntuple { gROOT->Reset(); Int_t nevent=0; // don't generate any events! TNtuple *ntuple = new TNtuple("ntuple","Demo ntuple","px:py"); for(Int_t i=0;i<nevent;i++) { ntuple->Fill(gRandom->Gaus(10.,2.5),gRandom->Gaus(0.,0.7)); } ntuple->Draw("px>>histo"); // I want to work with histogram (here just one example) histo->SetTitle("my histo"); } I use version 2.25/03 on Suse Linux. Miro
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