Fix Chi2Test: Support residuals for 2D/3D histograms #20798
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Fixed bug where Chi2Test only stored residuals for 1D histograms. For 2D/3D histograms, the residual array indexing ignored j and k loop indices, causing incorrect storage. Added resIndex counter for each comparison mode (UU, UW, WW) to properly index the residuals array for multi-dimensional histograms. Fixes root-project#20761
hageboeck
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Jan 7, 2026
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Hello, thanks for the contribution!
I think we could remove two unnecessary if (res). Please have a look if you agree.
Co-authored-by: Stephan Hageboeck <stephan.hageboeck@cern.ch>
Removed redundant if(res) checks Co-authored-by: Stephan Hageboeck <stephan.hageboeck@cern.ch>
Test Results 21 files 21 suites 3d 14h 17m 32s ⏱️ Results for commit f6053e7. |
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Description
Fixes #20761
This PR fixes a bug in
TH1::Chi2TestXwhere residuals were only correctly stored for 1D histograms. For 2D and 3D histograms, the residual array indexing only used theiloop index and ignoredjandk, causing incorrect storage.Changes
resIndexcounter for each of the three comparison modes (UU, UW, WW)res[i - i_start]withres[resIndex]in all three sectionsresIndex++increment after each residual is storedTesting
The fix ensures that residuals are stored sequentially for all bins in 2D/3D histograms, matching the order returned by
GetBin(i, j, k).Impact
Users can now retrieve residuals from
Chi2Testfor 2D and 3D histograms as originally intended by passing a residuals array.