Hi,
When I use THStack with histograms with variable bin sizes,
I've noticed that the bin edges get messed up somehow. The
problem can bre reproduced with the folliwng script:
{
gROOT->Reset();
Int_t nbins = 4;
Float_t lowEdge[5] = {0,1,2,2.5,3};
TH1F *h1 = new TH1F("nh1","blah",nbins,lowEdge);
THStack *hs = new THStack("nhs","stack");
hs->Add(h1);
hs->Draw();
for (Int_t i = 1; i <= nbins; i++) {
cout << "Bin " << i
<< ": Original histogram's low edge = "
<< h1->GetBinLowEdge(i)
<< "\t Stacked histo's low edge = "
<< hs->GetHistogram()->GetBinLowEdge(i)
<< endl;
}
}
This produces the output:
Bin 1: Original histogram's low edge = 0 Stacked histo's low edge = 0
Bin 2: Original histogram's low edge = 1 Stacked histo's low edge = 0.75
Bin 3: Original histogram's low edge = 2 Stacked histo's low edge = 1.5
Bin 4: Original histogram's low edge = 2.5 Stacked histo's low edge = 2.25
One can see the disagreement. Is this a bug or am I just missing
something subtle?
This is with ROOT version 3.05/04 on Red Hat 7.3.1. I realize
3.05/04 is not the current pro release --- I had a look at the
new release notes and didn't see any recent attempts to address
this problem.
Thanks a lot,
Andy
--
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Andy Hocker office: CDF trailer 168-O
University of Rochester phone: (630)-840-8622
Fermilab/CDF - M.S. 318 fax: (630)-840-2968
PO Box 500 e: hocker@fnal.gov
Batavia, IL 60510 hey ho: let's go
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