Hi Norbert, Instead of: root[0] hRecon = new TH1F("hRecon","hRecon",50,0,60); root[1] f2 = new TFile("/data4/calfiles/mt6125eve08_A.cal.root"); do root[0] f2 = new TFile("/data4/calfiles/mt6125eve08_A.cal.root"); root[1] hRecon = new TH1F("hRecon","hRecon",50,0,60); The problem is that TTree::Draw looks for an histogram named "hRecon" in the current directory. Rene Brun Norbert Danneberg wrote: > > Hi , > > I have a problem using the TTree:Draw in root 2.24/01. > > I create a new Histogram: > root[0] hRecon = new TH1F("hRecon","hRecon",50,0,60); > > open a file > root[1] f2 = new TFile("/data4/calfiles/mt6125eve08_A.cal.root") > > now I want to draw part of the tree into the histogram. > root[2] Events->Draw("TotalEnergy>>hRecon") > > Root creates a new canvas which contains a histogram with the data, > but the axis range is not from 0 to 60 as defined for the histo > "hRecon", > but automaticly choosen by TTree::Draw() > > But when I try to draw the histogram with > root[3] hRecon->Draw() > > the histogram is empty. > > Thanks, > Norbert > > -- > > Norbert Danneberg > > ETH Zurich - Institute for Particle Physics > Laboratory for Nuclear Physics Phone.: +41-1-633-2034 > Hoenggerberg Fax.: +41-1-633-1067 > CH-8093 Zurich > > ETH Zurich - Institute for Particle Physics > Paul Scherrer Institute Phone.: +41-56-310-3284 > CH-5232 Villigen PSI Fax.: +41-56-310-4362 > > email: Norbert.Danneberg@psi.ch
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