Hello,
is there a reason, why I cannot Draw a Histogram from a class?
Usually I’m using looper-classes generated by TTree::MakeClass, in order to do some quick analysis.
void discrete::Loop()
{
if (fChain == 0) return;
Long64_t nentries = fChain->GetEntriesFast();
TH1D *h= new TH1D("h","h",50,400,900);
Long64_t nbytes = 0, nb = 0;
for (Long64_t jentry=0; jentry<nentries;jentry++) {
Long64_t ientry = LoadTree(jentry);
if (ientry < 0) break;
nb = fChain->GetEntry(jentry); nbytes += nb;
// if (Cut(ientry) < 0) continue;
std::cout << "Filling " << VAL<< std::endl;
h->Fill(VAL);
}
}
h->Draw();
//gPad->Modified();
//gPad->Update();
}
This produces a canvas but no histogram. TGraphs are working, too.
If I am adding
TFile *f = new TFile("test.root","RECREATE");
TTree *tout = new TTree("tree","tree");
at the beginning of the method it suddenly works!
Bug or feature?
Georg
_ROOT Version:6.22.00
Platform: Windows 10
_Compiler: VS2019