Hi Martin, In order to refer to the leaf in a ntuple as a string for histogram filling purpose you should use TTree::Draw (or TTreeFormula for advanced users). The histogram class as no clue what so ever of the content of your TTree and can not make any correlation. Cheers, Philippe. -----Original Message----- From: owner-roottalk@pcroot.cern.ch [mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Martin Simard Sent: Wednesday, May 19, 2004 11:46 PM To: Rene Brun Cc: roottalk@pcroot.cern.ch Subject: Re: [ROOT] Fill histograms problem using TString Hi Rene, Thanks for the answer, but I want to use the TString like a leaf in a ntuple. For example, h1.Fill(track_number); // for example track_number is 1 or 2 TString s="track_number"; h2.Fill(s,1); // do not fill the integer value of track_number h1 gives 2 colonnes with values 1 or 2 and h2 give histograms with a colonne named track_number How can I do this properly to get h2 = h1 ? And is it possible... Thanks Martin On Sat, 15 May 2004, Rene Brun wrote: > Hi Martin, > > On Fri, 14 May 2004, Martin Simard wrote: > > > > > Hello, > > > > I want to fill histograms using TString like this. > > > > HistoName->Fill(Variable); > > > > Do Variable can be a TString?? > > Yes, you can, but must specify the weight argument > > TString s="Martin" > h.Fill(s,1); > > See an example in $ROOTSYS/tutorials/hlabels1.C > Don't forget to: > h.SetBit(TH1::kCanRebin); //before filling > h.LabelsDeflate(); // before drawing > > These two calls are automatically generated when projecting a > Tree string variable to a histogram. > > Rene Brun > > > > > > > I know there is a way to use a TString by Project like this. > > > > ntuple->Project(HistoName, Variable, weight(cut)); > > > > For this case, How can I use this in a Loop over all entries? > > > > > > Thanks > > Martin > > > >
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