Hi Rene! On Oct 13, 2004, at 8:54 AM, Rene Brun wrote: > Hi Roland, > > I agree with your comments about TTreeFormula. > This class is a key element of TTree::Draw, but it can also be used > independently. > It requires a much better documentation. > I tried to understand what's going on, and I must admit that I didn't really have enough brain memory to get a complete picture (at least not in a reasonable timeframe). From what I've seen TTreeFormula is always managed by a TTreeFormulaManager. I have already found out that the main use of this class is to manage the (up to four) expressions in the varexp of TTree::Draw plus the selection criterion, but from the code it is not immediately clear to me what the semantics are. What do I need to get it working reliably with a TChain? I'm currently looping with a custom MakeClass-generated class, filling my own arbirarily dimensioned histograms. Now I want to include a cut criterion, which should be parsed like a selection to TTree::Draw. I figure I need something a la in constructor: manager=new TTreeFormulaManager; in Loop(): cut=new TTreeFormula("some_name",cut,tree); manager->Add(cut); manager->Sync(); for(;;) { ii=LoadTree(i); fChain->GetEntry(ii); Double_t cut_result=cut->EvalInstance(); ... } manager->Remove(cut); manager->Sync(); I suppose I should also add manager->UpdateFormulaLeaves() to my ::Notify(), right? Is there something else which is needed? Thanks very much for your help! Ciao, Roland -- TU Muenchen, Physik-Department E18, James-Franck-Str. 85747 Garching Telefon 089/289-12592; Telefax 089/289-12570 -- A mouse is a device used to point at the xterm you want to type in. Kim Alm on a.s.r.
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