https://github.com/stdlib-js/math-base-special-xlogy
Compute `x * ln(y)` so that the result is `0` if `x = 0`.
https://github.com/stdlib-js/math-base-special-xlogy
javascript ln log logarithm math mathematics natural node node-js nodejs special stdlib
Last synced: 2 months ago
JSON representation
Compute `x * ln(y)` so that the result is `0` if `x = 0`.
- Host: GitHub
- URL: https://github.com/stdlib-js/math-base-special-xlogy
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-15T16:58:44.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2025-04-01T06:44:48.000Z (6 months ago)
- Last Synced: 2025-04-09T20:07:26.322Z (6 months ago)
- Topics: javascript, ln, log, logarithm, math, mathematics, natural, node, node-js, nodejs, special, stdlib
- Language: Python
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 840 KB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
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README
About stdlib...
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To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
# xlogy
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Compute `x * ln(y)` so that the result is `0` if `x = 0`.
## Installation
```bash
npm install @stdlib/math-base-special-xlogy
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var xlogy = require( '@stdlib/math-base-special-xlogy' );
```
#### xlogy( x, y )
Computes `x * ln(y)` so that the result is `0` if `x = 0`.
```javascript
var out = xlogy( 3.0, 2.0 );
// returns ~2.079
out = xlogy( 1.5, 5.9 );
// returns ~2.662
out = xlogy( 0.9, 1.0 );
// returns 0.0
out = xlogy( 0.0, -2.0 );
// returns 0.0
out = xlogy( 1.5, NaN );
// returns NaN
out = xlogy( 0.0, NaN );
// returns NaN
out = xlogy( NaN, 2.3 );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random-base-randu' );
var xlogy = require( '@stdlib/math-base-special-xlogy' );
var x;
var y;
var i;
for ( i = 0; i < 100; i++ ) {
x = randu();
if ( x < 0.5 ) {
x = 0.0;
}
y = ( randu() * 20.0 ) - 5.0;
console.log( 'xlogy(%d, %d) = %d', x, y, xlogy( x, y ) );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/math/base/special/xlogy.h"
```
#### stdlib_base_xlogy( x, y )
Computes `x * ln(y)` so that the result is `0` if `x = 0`.
```c
double v = stdlib_base_xlogy( 3.0, 2.0 );
// returns ~2.079
```
The function accepts the following arguments:
- **x**: `[in] double` input value.
- **y**: `[in] double` input value.
```c
double stdlib_base_xlogy( const double x, const double y );
```
### Examples
```c
#include "stdlib/math/base/special/xlogy.h"
#include
#include
int main( void ) {
double out;
double x;
double y;
int i;
for ( i = 0; i < 100; i++ ) {
x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
y = ( (double)rand() / (double)RAND_MAX ) * 5.0;
out = stdlib_base_xlogy( x, y );
printf( "xlogy(%lf, %lf) = %lf\n", x, y, out );
}
}
```
* * *
## See Also
- [`@stdlib/math-base/special/ln`][@stdlib/math/base/special/ln]: evaluate the natural logarithm of a double-precision floating-point number.
- [`@stdlib/math-base/special/xlog1py`][@stdlib/math/base/special/xlog1py]: compute `x * ln(y+1)` so that the result is `0` if `x = 0`.
* * *
## Notice
This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].
#### Community
[![Chat][chat-image]][chat-url]
---
## License
See [LICENSE][stdlib-license].
## Copyright
Copyright © 2016-2025. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/math-base-special-xlogy.svg
[npm-url]: https://npmjs.org/package/@stdlib/math-base-special-xlogy
[test-image]: https://github.com/stdlib-js/math-base-special-xlogy/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/math-base-special-xlogy/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-base-special-xlogy/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/math-base-special-xlogy?branch=main
[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg
[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im
[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/math-base-special-xlogy/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-xlogy/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-xlogy/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-xlogy/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-xlogy/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-xlogy/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-base-special-xlogy/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-xlogy/main/LICENSE
[@stdlib/math/base/special/ln]: https://github.com/stdlib-js/math-base-special-ln
[@stdlib/math/base/special/xlog1py]: https://github.com/stdlib-js/math-base-special-xlog1py