Evaluate the natural logarithm of 1+x.
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> Evaluate the [natural logarithm][@stdlib/math/base/special/ln] of 1+x.
``bash`
npm install @stdlib/math-base-special-log1p
`javascript`
var log1p = require( '@stdlib/math-base-special-log1p' );
#### log1p( x )
Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of 1+x.
`javascript
var v = log1p( 4.0 );
// returns ~1.609
v = log1p( -1.0 );
// returns -Infinity
v = log1p( Infinity );
// returns Infinity
v = log1p( 0.0 );
// returns 0.0
v = log1p( -0.0 );
// returns -0.0
v = log1p( NaN );
// returns NaN
`
For x < -1, the function returns NaN, as the [natural logarithm][@stdlib/math/base/special/ln] is not defined for negative numbers.
`javascript`
var v = log1p( -2.0 );
// returns NaN
`javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var log1p = require( '@stdlib/math-base-special-log1p' );
var opts = {
'dtype': 'float64'
};
var x = discreteUniform( 100, 0, 100, opts );
logEachMap( 'log1p( %0.4f ) = %0.4f', x, log1p );
`
*
`c`
#include "stdlib/math/base/special/log1p.h"
#### stdlib_base_log1p( x )
Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of 1+x.
`c
double out = stdlib_base_log1p( 4.0 );
// returns ~1.609
out = stdlib_base_log1p( -1.0 );
// returns -Infinity
`
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_log1p( const double x );
`c
#include "stdlib/math/base/special/log1p.h"
#include
#include
int main( void ) {
double x;
double v;
int i;
for ( i = 0; i < 100; i++ ) {
x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
v = stdlib_base_log1p( x );
printf( "log1p(%lf) = %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/log][@stdlib/math/base/special/log]: compute the base b logarithm of a double-precision floating-point number.
*
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].
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---
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[@stdlib/math/base/special/ln]: https://www.npmjs.com/package/@stdlib/math-base-special-ln
[@stdlib/math/base/special/log]: https://www.npmjs.com/package/@stdlib/math-base-special-log