log1mexp

Evaluates the natural logarithm of 1-exp(-|x|).

Installation

npm install @stdlib/math-base-special-log1mexp

Usage

var log1mexp = require( '@stdlib/math-base-special-log1mexp' );

log1mexp( x )

Evaluates the natural logarithm of 1-exp(-|x|).

var y = log1mexp( 0.0 );
// returns -Infinity

y = log1mexp( 5.0 );
// returns ~-0.00676

y = log1mexp( 10.0 );
// returns ~-0.00005

y = log1mexp( -10.0 );
// returns ~-0.00005

y = log1mexp( NaN );
// returns NaN

Examples

var incrspace = require( '@stdlib/array-base-incrspace' );
var log1mexp = require( '@stdlib/math-base-special-log1mexp' );

var x = incrspace( -10.0, 10.0, 0.01 );

var i;
for ( i = 0; i < x.length; i++ ) {
    console.log( 'x: %d, f(x): %d', x[ i ], log1mexp( x[ i ] ) );
}

C APIs

Usage

#include "stdlib/math/base/special/log1mexp.h"

stdlib_base_log1mexp( x )

Evaluates the natural logarithm of 1-exp(-|x|).

double out = stdlib_base_log1mexp( 10.0 );
// returns ~-0.00005

out = stdlib_base_log1mexp( 5.0 );
// returns ~-0.00676

The function accepts the following arguments:

• x: [in] double input value.

double stdlib_base_log1mexp( const double x );

Examples

#include "stdlib/math/base/special/log1mexp.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double x;
    double v;
    int i;
    
    for ( i = 0; i < 100; i++ ) {
        x = ( ( (double)rand() / (double)RAND_MAX ) * 20.0 ) - 10.0;
        v = stdlib_base_log1mexp( x );
        printf( "x: %lf, f(x): %lf\n", x, v );
    }
}

See Also

• @stdlib/math-base/special/exp: natural exponential function.
• @stdlib/math-base/special/ln: evaluate the natural logarithm of a double-precision floating-point number.
• @stdlib/math-base/special/log1p: evaluate the natural logarithm of 1+x.
• @stdlib/math-base/special/log1pexp: evaluate the natural logarithm of 1+exp(x).

Notice

This package is part of 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, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.