Evaluate ln(1+x) - x.
npm install @stdlib/math-base-special-log1pmxWe believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js. The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases. When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there. 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!
About stdlib...
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Evaluate ln(1+x) - x.
``bash`
npm install @stdlib/math-base-special-log1pmx
`javascript`
var log1pmx = require( '@stdlib/math-base-special-log1pmx' );
#### log1pmx( x )
Evaluates ln(1+x) - x.
`javascript
var v = log1pmx( 1.1 );
// returns ~-0.358
v = log1pmx( 0.99 );
// returns ~-0.302
v = log1pmx( -0.99 );
// returns ~-3.615
v = log1pmx( -1.1 );
// returns NaN
v = log1pmx( NaN );
// returns NaN
`
`javascript
var incrspace = require( '@stdlib/array-base-incrspace' );
var log1pmx = require( '@stdlib/math-base-special-log1pmx' );
var x = incrspace( 0.0, 10.0, 0.01 );
var i;
for ( i = 0; i < x.length; i++ ) {
console.log( 'x: %d, f(x): %d', x[ i ], log1pmx( x[ i ] ) );
}
`
*
`c`
#include "stdlib/math/base/special/log1pmx.h"
#### stdlib_base_log1pmx( x )
Evaluates ln(1+x) - x.
`c`
double out = stdlib_base_log1pmx( 1.1 );
// returns ~-0.358
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_log1pmx( const double x );
`c
#include "stdlib/math/base/special/log1pmx.h"
#include
#include
int main( void ) {
double x;
double v;
int i;
for ( i = 0; i < 100; i++ ) {
x = ( (double)rand() / (double)RAND_MAX ) * 10.0;
v = stdlib_base_log1pmx( x );
printf( "x: %lf, f(x): %lf\n", x, v );
}
}
`
*
- [@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/log1p][@stdlib/math/base/special/log1p]: evaluate the natural logarithm of 1+x.
*
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]
---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/math-base-special-log1pmx.svg
[npm-url]: https://npmjs.org/package/@stdlib/math-base-special-log1pmx
[test-image]: https://github.com/stdlib-js/math-base-special-log1pmx/actions/workflows/test.yml/badge.svg?branch=v0.2.4
[test-url]: https://github.com/stdlib-js/math-base-special-log1pmx/actions/workflows/test.yml?query=branch:v0.2.4
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-base-special-log1pmx/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/math-base-special-log1pmx?branch=main
[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg
[chat-url]: https://stdlib.zulipchat.com
[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-log1pmx/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-log1pmx/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-log1pmx/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-log1pmx/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-log1pmx/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-log1pmx/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-base-special-log1pmx/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-log1pmx/main/LICENSE
[@stdlib/math/base/special/ln]: https://www.npmjs.com/package/@stdlib/math-base-special-ln
[@stdlib/math/base/special/log1p]: https://www.npmjs.com/package/@stdlib/math-base-special-log1p