Roland, A TChain is a TTree. So everything working on TTree should also work with TChain. Rene Brun On Thu, 14 Oct 2004, Roland Kuhn wrote: > 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. >
This archive was generated by hypermail 2b29 : Sun Jan 02 2005 - 05:50:10 MET