log1pexp

Evaluates the natural logarithm of 1+exp(x).

Usage

var log1pexp = require( '@stdlib/math/base/special/log1pexp' );

log1pexp( x )

Evaluates the natural logarithm of 1+exp(x).

var y = log1pexp( -10.0 );
// returns ~0.000045

y = log1pexp( 0.0 );
// returns ~0.693147

y = log1pexp( 5.0 );
// returns ~5.006715

y = log1pexp( 34.0 );
// returns 34.0

y = log1pexp( NaN );
// returns NaN

Examples

var incrspace = require( '@stdlib/array/base/incrspace' );
var log1pexp = require( '@stdlib/math/base/special/log1pexp' );

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 ], log1pexp( x[ i ] ) );
}

C APIs

Usage

#include "stdlib/math/base/special/log1pexp.h"

stdlib_base_log1pexp( x )

Evaluates the natural logarithm of 1+exp(x).

double out = stdlib_base_log1pexp( 5.0 );
// returns ~5.006715

out = stdlib_base_log1pexp( 34.0 );
// returns 34.0

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_log1pexp( const double x );

Examples

#include "stdlib/math/base/special/log1pexp.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_log1pexp( x );
        printf( "x: %lf, f(x): %lf\n", x, v );
    }
}