feat: add `stats/base/dists/halfnormal/entropy` #9753

bhargava-d16 · 2026-01-14T22:18:21Z

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Progresses #9416

Description

What is the purpose of this pull request?

This pull request:

This PR adds implementation of entropy calculation for half-normal distribution.

Related Issues

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This pull request has the following related issues:

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

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No.

Other

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No.

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Read, understood, and followed the contributing guidelines.

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I consulted ChatGPT to verify mathematical formulation of half-normal entropy function and to confirm expected numerical values

@stdlib-js/reviewers

--- 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 ---

stdlib-bot · 2026-01-14T22:21:08Z

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/halfnormal/entropy	$\color{green}164/164$ $\color{green}+0.00%$	$\color{green}8/8$ $\color{green}+0.00%$	$\color{green}2/2$ $\color{green}+0.00%$	$\color{green}164/164$ $\color{green}+0.00%$

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

Planeshifter

Thanks for this PR! Left initial comment.

Planeshifter · 2026-01-14T23:32:10Z

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

+// returns ~2.6238370975295946
+```
+
+If provided `sigma < 0`, the function returns `NaN`.


The documentation says sigma < 0 but the implementation in lib/main.js checks sigma <= 0.0. This should be updated to sigma <= 0 to match the implementation behavior (sigma=0 also returns NaN).

Note: docs/repl.txt correctly uses σ ≤ 0.

Planeshifter · 2026-01-14T23:32:11Z

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

+
+```c
+double out = stdlib_base_dists_halfnormal_entropy( 1.0 );
+// returns ~0.726


The expected output value ~0.726 is incorrect. For sigma=1.0, the entropy should be ~1.0143991850954939 (as shown correctly in the JavaScript examples above).

double out = stdlib_base_dists_halfnormal_entropy( 1.0 ); // returns ~1.014

Planeshifter · 2026-01-14T23:32:12Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/entropy/docs/types/index.d.ts

+*
+* ## Notes
+*
+* -   If provided `σ < 0`, the function returns `NaN`.


The documentation says σ < 0 but the implementation checks σ <= 0. This should be updated to σ ≤ 0 to match the implementation behavior (sigma=0 also returns NaN).

Note: docs/repl.txt correctly uses σ ≤ 0.

Planeshifter · 2026-01-15T01:56:51Z

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

+var y = entropy( 1.0 );
+// returns ~1.0143991850954939
+
+y = entropy( 5.0 );
+// returns ~2.6238370975295946


Suggested change

var y = entropy( 1.0 );

// returns ~1.0143991850954939

y = entropy( 5.0 );

// returns ~2.6238370975295946

var y = entropy( 1.0 );

// returns ~1.014

y = entropy( 5.0 );

// returns ~2.624

--- 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: 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: na - task: lint_javascript_benchmarks status: na - task: lint_python status: na - 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: passed - task: lint_license_headers status: passed ---

Planeshifter · 2026-01-16T05:16:28Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/entropy/docs/repl.txt

@@ -0,0 +1,26 @@
+{{alias}}( σ )


The file should start with a leading blank line before {{alias}}.

Suggested change

{{alias}}( σ )

{{alias}}( σ )

Planeshifter · 2026-01-16T05:16:30Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/entropy/docs/types/index.d.ts

+* var v = entropy( 1.0 );
+* // returns ~1.0143991850954939
+*
+* @example
+* var v = entropy( 5.0 );
+* // returns ~2.6238370975295946


Same as the repl.txt - the example return values should use short approximations instead of full precision. Reference packages (e.g., rayleigh/entropy) use // returns ~3.139 rather than the full value.

Suggested change

* var v = entropy( 1.0 );

* // returns ~1.0143991850954939

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.6238370975295946

* var v = entropy( 1.0 );

* // returns ~1.014

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.624

Planeshifter · 2026-01-16T05:16:32Z

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

+	for ( i = 0; i < expected.length; i++ ) {
+		y = entropy( sigma[ i ] );
+		if ( y === expected[ i ] ) {
+			t.strictEqual(y, expected[ i ], 'sigma: '+sigma[i]+', y: '+y+', expected: '+expected[i]);


Missing space after t.strictEqual( - should be t.strictEqual( y, with a space after the opening parenthesis, matching stdlib's spacing convention.

Suggested change

t.strictEqual(y, expected[ i ], 'sigma: '+sigma[i]+', y: '+y+', expected: '+expected[i]);

t.strictEqual( y, expected[ i ], 'sigma: '+sigma[i]+', y: '+y+', expected: '+expected[i] );

Planeshifter · 2026-01-16T05:16:33Z

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

+		} else {
+			delta = abs( y - expected[ i ] );
+			tol = 40.0 * EPS * abs( expected[ i ] );
+			t.ok(delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.');


Missing space after t.ok( - should be t.ok( delta with a space after the opening parenthesis.

Suggested change

t.ok(delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.');

t.ok( delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.' );

Planeshifter · 2026-01-16T05:16:34Z

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

+		} else {
+			delta = abs( y - expected[ i ] );
+			tol = 40.0 * EPS * abs( expected[ i ] );
+			t.ok(delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.');


Missing space after t.ok( - should be t.ok( delta with a space after the opening parenthesis.

Suggested change

t.ok(delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.');

t.ok( delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.' );

Planeshifter · 2026-01-16T05:22:19Z

lib/node_modules/@stdlib/stats/base/dists/halfnormal/entropy/docs/repl.txt

+    > var v = {{alias}}( 1.0 )
+    ~1.0143991850954939
+    > v = {{alias}}( 5.0 )
+    ~2.6238370975295946


The example output values should use short approximations instead of full precision. Looking at other stdlib repl.txt files (e.g., rayleigh/entropy), they use formats like ~3.34 and ~2.446 rather than ~1.0143991850954939.

Suggested change

> var v = {{alias}}( 1.0 )

~1.0143991850954939

> v = {{alias}}( 5.0 )

~2.6238370975295946

> var v = {{alias}}( 1.0 )

~1.014

> v = {{alias}}( 5.0 )

~2.624

Planeshifter · 2026-01-16T05:23:15Z

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

+* var v = entropy( 1.0 );
+* // returns ~1.0143991850954939
+*
+* v = entropy( 5.0 );
+* // returns ~2.6238370975295946


Suggested change

* var v = entropy( 1.0 );

* // returns ~1.0143991850954939

*

* v = entropy( 5.0 );

* // returns ~2.6238370975295946

* var v = entropy( 1.0 );

* // returns ~1.014

*

* v = entropy( 5.0 );

* // returns ~2.624

Planeshifter · 2026-01-16T05:23:31Z

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

+* var v = entropy( 1.0 );
+* // returns ~1.0143991850954939
+*
+* @example
+* var v = entropy( 5.0 );
+* // returns ~2.6238370975295946


Suggested change

* var v = entropy( 1.0 );

* // returns ~1.0143991850954939

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.6238370975295946

* var v = entropy( 1.0 );

* // returns ~1.014

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.624

Planeshifter · 2026-01-16T05:23:48Z

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

+* var v = entropy( 1.0 );
+* // returns ~1.0143991850954939
+*
+* @example
+* var v = entropy( 5.0 );
+* // returns ~2.6238370975295946


Suggested change

* var v = entropy( 1.0 );

* // returns ~1.0143991850954939

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.6238370975295946

* var v = entropy( 1.0 );

* // returns ~1.014

*

* @example

* var v = entropy( 5.0 );

* // returns ~2.624

Planeshifter · 2026-01-16T05:24:07Z

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

+* double y = stdlib_base_dists_halfnormal_entropy( 1.0 );
+* // returns ~1.0143991850954939


Suggested change

* double y = stdlib_base_dists_halfnormal_entropy( 1.0 );

* // returns ~1.0143991850954939

* double y = stdlib_base_dists_halfnormal_entropy( 1.0 );

* // returns ~1.014

--- 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: passed - task: lint_javascript_src status: passed - 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: 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: passed - task: lint_license_headers status: passed ---

--- 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: na - task: lint_javascript_benchmarks status: na - task: lint_python status: na - 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 ---

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stdlib-bot added Statistics Issue or pull request related to statistical functionality. Needs Review A pull request which needs code review. labels Jan 14, 2026

Planeshifter requested changes Jan 15, 2026

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Planeshifter changed the title ~~feat: add stats/base/dists/halfnormal/entropy~~ feat: add stats/base/dists/halfnormal/entropy Jan 15, 2026

bhargava-d16 requested a review from Planeshifter January 15, 2026 04:24

Planeshifter requested changes Jan 16, 2026

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bhargava-d16 added 2 commits January 16, 2026 05:58

bhargava-d16 requested a review from Planeshifter January 16, 2026 07:34

Neerajpathak07 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

	t.strictEqual(y, expected[ i ], 'sigma: '+sigma[i]+', y: '+y+', expected: '+expected[i]);
	t.strictEqual( y, expected[ i ], 'sigma: '+sigma[i]+', y: '+y+', expected: '+expected[i] );

	t.ok(delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.');
	t.ok( delta <= tol, 'within tolerance. sigma: '+sigma[i]+'. y: '+y+'. E: '+expected[i]+'. Δ: '+delta+'. tol: '+tol+'.' );

		* double y = stdlib_base_dists_halfnormal_entropy( 1.0 );
		* // returns ~1.0143991850954939

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feat: add stats/base/dists/halfnormal/entropy #9753

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bhargava-d16 commented Jan 14, 2026

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feat: add `stats/base/dists/halfnormal/entropy` #9753

feat: add `stats/base/dists/halfnormal/entropy` #9753

stdlib-bot commented Jan 14, 2026 •

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