GH-16757: Fix top_n_features in shap_summary_plot in R

[tomasfryda]

#16757

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

Fixes an off-by-one issue in the R h2o.shap_summary_plot feature-selection logic so top_n_features renders exactly the requested number of features, and adds regression tests in both R and Python.

Changes:

• Fix top_n_features slicing in h2o.shap_summary_plot (R) and drop unused factor levels before selecting features.
• Add an R unit test covering typical and corner-case top_n_features values (including 0 erroring and -1 meaning “all”).
• Add a Python unit test intended to validate top_n_features behavior via plotted y-axis labels.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
h2o-r/tests/testdir_misc/explain/runit_shap_summary_plot_top_n_features.R	Adds R regression tests for top_n_features sizing and corner cases.
h2o-r/h2o-package/R/explain.R	Fixes off-by-one feature selection and adds top_n_features == 0 validation.
h2o-py/tests/testdir_misc/explain/pyunit_shap_summary_plot_top_n_features.py	Adds Python regression test that inspects rendered tick labels to count displayed features.

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