log1mexp

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

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 );
    }
}