Hi, I want to create a TClonesArray with pointers to histograms. Later I need to fill these histograms in a loop from a tree with the >> . First I excersided this root [0] TH1F* b = new TH1F("bname","btitle",40,-20.,200); root [1] b->Draw(); Warning in <MakeDefCanvas>: creating a default canvas with name c1 o.k. this worked, but now root [2] TClonesArray* tps = new TClonesArray("TH1F",5); root [3] dummy = new(tps[0]) TH1F("bname0","btitle0",40,-20.,200); root [4] tps[0]->Draw(); Warning in <MakeDefCanvas>: creating a default canvas with name c1 *** Break *** segmentation violation ( 0) 0xc14f5d40 StackTrace__11TUnixSystemFv + 0x28 [/afs/cern.ch/na49/library/local/ROOT/hpux10aCC/root/lib/libUnix.sl] this did not work. Also bname0->Draw() does not work. (I do not know exactly why the new operator with placement requires a syntax like `dummy new() ..', I use it in other programs without `dummy', but CINT would complain..). Later I want to iterate over the histogram objects in the TClonesArray like Float_t tEntries[5]; Char_t tWhat[30]; for(Int_t s = 0; s < 5; s++) { sprintf(tWhat,"fTPS%d>>bname%d",s); // fTPS is leave in my TTree T T->Draw(tWhat,""); tEntries[s] = tps[s]->GetIntegral(); // also access other properties here } .. which did not work so far. Is there an example how to iterate through a TClonesArray with histograms and fill them from e.g. a TTree or TNtuple? I also need to access the histograms like in tps[s]->GetIntegral() thanks for any help Dirk
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