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
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> --
> A mouse is a device used to point at
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> Kim Alm on a.s.r.
>
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