Subset of 2D histogram

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Hi @diboye,

there is quite some confusion with the indices there :slight_smile:

I think the easiest would be to:

  • Figure out the bin coordinates for each bin in your new subset histogram
  • Look up the bin content for that coordinates in the full hist
  • Set the bin content (and maybe errors too) of the subset histogram accordingly
TFile* file = TFile::Open(
    "BRscaled_gaussiansignal_4echannel_mZd31_mH108GeV.root");

TH2F* tempHist2D = file->Get<TH2F>("Nominal/sig");
TH2D* tempHist2DBis =
    new TH2D("tempHist2DBis", "", 2, 105, 111, 2, 30, 32);

// Starting with 1 because bin zero is the underflow bin
for (int i = 1; i <= tempHist2DBis->GetNbinsX(); i++) {
  for (int j = 1; j <= tempHist2DBis->GetNbinsY(); j++) {
    double x = tempHist2DBis->GetXaxis()->GetBinCenter(i);
    double y = tempHist2DBis->GetYaxis()->GetBinCenter(j);
    double content =
        tempHist2D->GetBinContent(tempHist2D->FindBin(x, y));
    tempHist2DBis->SetBinContent(i, j, 0, content);
  }
}

tempHist2DBis->Draw("colz text");

plot
plot696×472 5.85 KB

I hope that helps!

Cheers,
Jonas

PS: Not I added text to the bins in the drawing, which is quite useful for checks.