Hi, This feature 'could' be added to the TTree::Draw mechanism but it would not be trivial. A better alternative in your case is to use the MakeClass feature that would give you a much wider range of possibilities to create and fill your histogram (See TTree::MakeClass). Philippe. > -----Original Message----- > From: owner-roottalk@pcroot.cern.ch > [mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Marcelo G. Munhoz > Sent: Friday, August 11, 2000 12:46 PM > To: roottalk > Subject: [ROOT] arrays in TTree > > > > Hi, > > I have a TTree composed of TClonesArray objects (TBranchClones). > From the documentation (and empirically), I noticed that is possible to > refer to a specific element of my array using the [ ] operator. So, for > instance, let's say my TTree has two branchs of TClonesArray called > clone1 and clone2. The object clone1 has data members a1 and b1, while > the object clone2 has data members a2 and b2. Now, I can do something > like: > > myTree->Draw("clone1.a1:clone2.a2[2]") > > i.e., I can draw all elements a1 from clone1 as a function of the > specific element a2[2] from clone2. However, that's not exactly what I > want to do. Instead of drawing always a2[2] in the x-axis, I'd like to > select the element of a2 with a index given by b1, i.e., b1 is a index > refering to the TClonesArray clone2. So, what I'd like to do is: > > myTree->Draw("clone1.a1:clone2.a2[clone1.b1]") > > I've tried this syntax and it does not work. Unless you introduce a > number between [ ], ROOT totally ignores what is inside. > > My question is: is there anyway to go around this limitation? I'd > like also to use such thing for selection. For instance, to do something > like: > > myTree->Draw("clone1.a1","clone2.a2[clone1.b1]>0") > > > Maybe my problem is too specific, but if someone had similar > experience, I'd apreciate any help. And I hope my explanation is not too > confusing... > > Thanks for any help, > > Marcelo. > > > > >
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