Andy Haas wrote: > > I'm running version 1.02 on WinNT. > > In trying to create a 3D Histogram from a saved ntuple, I've done the > following but it crashes: > > { > f1 = new TFile("haas.root"); > h3 = new TH3F("h3" , "3-D Histogram" ,250,0,25,250,0,25,250,0,50); > ntuple->EventLoop(3,h3); > } > > What am I doing wrong? > Thanks in adavnce, Andy. The facility to fill an already existing 3-D histogram from an ntuple is not implemented. Some TTree functions like TTree::Draw, EventLoop are ready for 3-D histograms, but not the auxiliary functions TakeAction and Estimate. You should not call TTree::EventLoop directly (this function should be protected in fact). To loop on a Tree, use the functions Draw or Loop. The reason why your example crash, I think, is that you create a 3-D histogram with 250 channels in x,y and z. This requires about 62Mbytes of main memory! What you can do is to produce a 3-d scatter plot with a command such as ntuple->Draw("x:y"z) Rene Brun
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