ln

Evaluate the natural logarithm of a double-precision floating-point number.

Usage

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

ln( x )

Evaluates the natural logarithm of a double-precision floating-point number.

var v = ln( 4.0 );
// returns ~1.386

v = ln( 0.0 );
// returns -Infinity

v = ln( Infinity );
// returns Infinity

v = ln( NaN );
// returns NaN

For negative numbers, the natural logarithm is not defined.

var v = ln( -4.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var ln = require( '@stdlib/math/base/special/ln' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = round( randu() * 100.0 );
    console.log( 'ln(%d) = %d', x, ln( x ) );
}

C APIs

Usage

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

stdlib_base_ln( x )

Evaluates the natural logarithm of a double-precision floating-point number.

double v = stdlib_base_ln( 2.0 );
// returns ~0.693

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_ln( const double x );

Examples

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

int main( void ) {
    double out;
    double x;
    int i;

    for ( i = 0; i < 100; i++ ) {
        x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
        out = stdlib_base_ln( x );
        printf( "ln(%lf) = %lf\n", x, out );
    }
}