2

Edit: this is a version problem. Uproot 4.3.7 produces the expected result, while the error below occurred in 4.0.0

I am creating 1-D histograms in ROOT with non-uniform bin sizes, then accessing them with uproot. The bin edges are not returned properly by uproot.

Creating test histogram (tested with root 6.22/06):

{

  TFile *f = new TFile("uproot_test.root","new");
  Double_t binedges[6] = {0.1, 0.158489, 0.251189, 0.398107, 0.630957, 1};
  TH1D *h = new TH1D("hist","hist",5, binedges);
  h->Write();
  f->Close();

  //reopen and print bins to verify they're right in root file
  TFile *f2 = new TFile("uproot_test.root");
  TH1D *h2 = (TH1D*)f2->Get("hist");
  TArrayD binEdges = *(h2->GetXaxis()->GetXbins());
  
  for (Int_t iX = 0; iX < binEdges.GetSize(); iX++) {
    std::cout << binEdges[iX] << std::endl;
  }
}

This produces the input bin edges as output: 0.1 0.158489 0.251189 0.398107 0.630957 1

Now, read with uproot 4.0.0 (running python 3.8.5)

import uproot

f = uproot.open('uproot_test.root')
h = f['hist']
print(h.axis().edges())

Bin edges output: [0.1 0.28 0.46 0.64 0.82 1. ]

It appears that uproot is grabbing the first and last bin edge and assuming a linear spacing in between, which is clearly the wrong behavior in this case. Is this a true bug? An option that I can't find? Some incompatibility between code versions?

Daniel Coupland
  • 21
  • 2
  • It's an already-fixed bug: in the latest Uproot, `h.axis().edges()` prints the same values as ROOT. (Uproot 4.0.0 was released Dec 5, 2020; there have been 43 releases since then!) Also, bugs should be reported in [GitHub Issues](https://github.com/scikit-hep/uproot5/issues). Thanks! – Jim Pivarski Oct 25 '22 at 18:48
  • Thanks, I updated and confirmed that uproot 4.3.7 produces the correct output. – Daniel Coupland Oct 27 '22 at 15:25

0 Answers0