feat: add implementation of `stats/base/dists/halfnormal/kurtosis` #9771

Om-A-osc · 2026-01-15T18:35:14Z

type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes. report:

task: lint_filenames status: passed
task: lint_editorconfig status: passed
task: lint_markdown status: passed
task: lint_package_json status: passed
task: lint_repl_help status: passed
task: lint_javascript_src status: passed
task: lint_javascript_cli status: na
task: lint_javascript_examples status: passed
task: lint_javascript_tests status: passed
task: lint_javascript_benchmarks status: passed
task: lint_python status: na
task: lint_r status: na
task: lint_c_src status: missing_dependencies
task: lint_c_examples status: missing_dependencies
task: lint_c_benchmarks status: missing_dependencies
task: lint_c_tests_fixtures status: na
task: lint_shell status: na
task: lint_typescript_declarations status: passed
task: lint_typescript_tests status: passed
task: lint_license_headers status: passed ---

Resolves #9416.

Description

What is the purpose of this pull request?

This pull request:

Adds an implementation of excess kurtosis for the half-normal distribution.
Uses the closed-form analytic expression , which is independent of the scale parameter.
Introduces corresponding fixtures, documentation, tests, and REPL examples.
Ensures consistency with existing stdlib distribution implementations and linting rules.

Related Issues

Does this pull request have any related issues?

This pull request progresses the following related issue:

[RFC]: Tracking issue for complete implementation of @stdlib/stats/base/dists/halfnormal package #9416

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

Yes
No

If you answered "yes" above, how did you use AI assistance?

Code generation (e.g., when writing an implementation or fixing a bug)
Test/benchmark generation
Documentation (including examples)
Research and understanding

Disclosure

I used llm , wikipedia and other mathematical websites in a limited capacity to verify the mathematical formula for half-normal excess kurtosis and to cross-check references. All code, tests, and documentation were authored manually.

@stdlib-js/reviewers

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Planeshifter

Thanks for opening this PR!

Planeshifter · 2026-01-16T00:23:24Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/lib/main.js

+// VARIABLES //
+
+var PI = require( '@stdlib/constants/float64/pi' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );


This section header should be // MODULES // since it contains require statements. The // VARIABLES // section is for computed constants and other variable declarations.

Suggested change

// VARIABLES //

var PI = require( '@stdlib/constants/float64/pi' );

var isnan = require( '@stdlib/math/base/assert/is-nan' );

// MODULES //

var PI = require( '@stdlib/constants/float64/pi' );

var isnan = require( '@stdlib/math/base/assert/is-nan' );

Planeshifter · 2026-01-16T00:23:26Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/src/main.c

+	) {
+		return 0.0 / 0.0; // NaN
+	}
+	return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) *( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );


Missing space before the multiplication operator. Let's match the stdlib C style guide.

Suggested change

return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) *( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );

return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) * ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );

Planeshifter · 2026-01-16T00:23:27Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/benchmark/benchmark.js

+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		// Generate valid scale parameters:
+		sigma = ( randu() * 10.0 ) + 0.1;
+		y = kurtosis( sigma );


The random data generation should happen outside the timing loop. Per latest stdlib benchmark conventions, pre-generate values before b.tic() and cycle through them using modulo indexing.

Planeshifter · 2026-01-16T00:23:28Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/package.json

+  "directories": {
+    "benchmark": "./benchmark",
+    "doc": "./docs",
+    "example": "./examples",
+    "lib": "./lib",
+    "test": "./test"
+  },


Since this package has a C implementation with a .gyp file, we need to add "gypfile": true and include the include and src directories. See @stdlib/stats/base/dists/levy/pdf/package.json for reference.

The directories section should look like:

"directories": { "benchmark": "./benchmark", "doc": "./docs", "example": "./examples", "include": "./include", "lib": "./lib", "src": "./src", "test": "./test" }

And add "gypfile": true after line 16.

Planeshifter · 2026-01-16T00:23:29Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/test/test.native.js

+	sigma = data.sigma;
+	for ( i = 0; i < sigma.length; i++ ) {
+		y = kurtosis( sigma[i] );
+		if ( expected[i] !== null) {


Missing space before the closing parenthesis to match stdlib style.

Suggested change

if ( expected[i] !== null) {

if ( expected[i] !== null ) {

Planeshifter · 2026-01-16T00:23:30Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/examples/index.js

+for ( i = 0; i < 10; i++ ) {
+	sigma = randu() * 20.0;
+	y = kurtosis( sigma );
+	console.log( 'σ: %lf, Kurt(σ): %lf', sigma, y );


JavaScript's console.log doesn't interpret %lf as a format specifier - it just prints it literally. Use %d for numbers instead.

Suggested change

console.log( 'σ: %lf, Kurt(σ): %lf', sigma, y );

console.log( 'σ: %d, Kurt(σ): %d', sigma, y );

Planeshifter · 2026-01-16T00:23:31Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/README.md

+for ( i = 0; i < 10; i++ ) {
+    sigma = randu() * 20.0;
+    y = kurtosis( sigma );
+    console.log( 'σ: %lf, Kurt(σ): %lf', sigma, y );


Same issue here - %lf won't work as a format specifier in JavaScript. Use %d instead.

Suggested change

console.log( 'σ: %lf, Kurt(σ): %lf', sigma, y );

console.log( 'σ: %d, Kurt(σ): %d', sigma, y );

Planeshifter · 2026-01-16T00:23:38Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/benchmark/benchmark.js

+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});


This package is missing benchmark/benchmark.native.js which is needed for benchmarking the native addon. See @stdlib/stats/base/dists/levy/pdf/benchmark/benchmark.native.js for a reference implementation.

stdlib-bot · 2026-01-16T00:53:31Z

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/halfnormal/kurtosis	$\color{green}153/153$ $\color{green}+100.00%$	$\color{green}7/7$ $\color{green}+100.00%$	$\color{green}2/2$ $\color{green}+100.00%$	$\color{green}153/153$ $\color{green}+100.00%$

The above coverage report was generated for the changes in this PR.

--- type: pre_commit_static_analysis_report description: Results of running static analysis checks when committing changes. report: - task: lint_filenames status: passed - task: lint_editorconfig status: passed - task: lint_markdown status: passed - task: lint_package_json status: passed - task: lint_repl_help status: na - task: lint_javascript_src status: passed - task: lint_javascript_cli status: na - task: lint_javascript_examples status: passed - task: lint_javascript_tests status: passed - task: lint_javascript_benchmarks status: passed - task: lint_python status: na - task: lint_r status: na - task: lint_c_src status: missing_dependencies - task: lint_c_examples status: na - task: lint_c_benchmarks status: na - task: lint_c_tests_fixtures status: na - task: lint_shell status: na - task: lint_typescript_declarations status: passed - task: lint_typescript_tests status: na - task: lint_license_headers status: passed ---

Om-A-osc · 2026-01-16T10:03:41Z

@Planeshifter I’ve addressed the requested changes. I’d appreciate it if you could take another look when convenient thanks again for your help.

--- type: pre_commit_static_analysis_report description: Results of running static analysis checks when committing changes. report: - task: lint_filenames status: passed - task: lint_editorconfig status: passed - task: lint_markdown status: na - task: lint_package_json status: na - task: lint_repl_help status: na - task: lint_javascript_src status: na - task: lint_javascript_cli status: na - task: lint_javascript_examples status: na - task: lint_javascript_tests status: passed - task: lint_javascript_benchmarks status: na - task: lint_python status: missing_dependencies - task: lint_r status: na - task: lint_c_src status: na - task: lint_c_examples status: na - task: lint_c_benchmarks status: na - task: lint_c_tests_fixtures status: na - task: lint_shell status: na - task: lint_typescript_declarations status: passed - task: lint_typescript_tests status: na - task: lint_license_headers status: passed ---

stdlib-bot added Statistics Issue or pull request related to statistical functionality. First-time Contributor A pull request from a contributor who has never previously committed to the project repository. Needs Review A pull request which needs code review. labels Jan 15, 2026

Planeshifter requested changes Jan 16, 2026

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stdlib-bot added the Potential Duplicate There might be another pull request resolving the same issue. label Jan 16, 2026

Planeshifter added Needs Changes Pull request which needs changes before being merged. and removed Needs Review A pull request which needs code review. labels Jan 16, 2026

Om-A-osc requested a review from Planeshifter January 16, 2026 18:13

stdlib-bot added the Needs Review A pull request which needs code review. label Jan 16, 2026

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	return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) *( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );
	return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) * ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );

	console.log( 'σ: %lf, Kurt(σ): %lf', sigma, y );
	console.log( 'σ: %d, Kurt(σ): %d', sigma, y );

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feat: add implementation of `stats/base/dists/halfnormal/kurtosis` #9771

feat: add implementation of `stats/base/dists/halfnormal/kurtosis` #9771