xlogy

Compute x * ln(y) so that the result is 0 if x = 0.

Installation

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

Usage

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

xlogy( x, y )

Computes x * ln(y) so that the result is 0 if x = 0.

var out = xlogy( 3.0, 2.0 );
// returns ~2.079

out = xlogy( 1.5, 5.9 );
// returns ~2.662

out = xlogy( 0.9, 1.0 );
// returns 0.0

out = xlogy( 0.0, -2.0 );
// returns 0.0

out = xlogy( 1.5, NaN );
// returns NaN

out = xlogy( 0.0, NaN );
// returns NaN

out = xlogy( NaN, 2.3 );
// returns NaN

Examples

var randu = require( '@stdlib/random-base-randu' );
var xlogy = require( '@stdlib/math-base-special-xlogy' );

var x;
var y;
var i;

for ( i = 0; i < 100; i++ ) {
    x = randu();
    if ( x < 0.5 ) {
        x = 0.0;
    }
    y = ( randu() * 20.0 ) - 5.0;
    console.log( 'xlogy(%d, %d) = %d', x, y, xlogy( x, y ) );
}

C APIs

Usage

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

stdlib_base_xlogy( x, y )

Computes x * ln(y) so that the result is 0 if x = 0.

double v = stdlib_base_xlogy( 3.0, 2.0 );
// returns ~2.079

The function accepts the following arguments:

• x: [in] double input value.
• y: [in] double input value.

double stdlib_base_xlogy( const double x, const double y );

Examples

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

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

    for ( i = 0; i < 100; i++ ) {
        x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
        y = ( (double)rand() / (double)RAND_MAX ) * 5.0;
        out = stdlib_base_xlogy( x, y );
        printf( "xlogy(%lf, %lf) = %lf\n", x, y, out );
    }
}

See Also

• @stdlib/math-base/special/ln: evaluate the natural logarithm of a double-precision floating-point number.
• @stdlib/math-base/special/xlog1py: compute x * ln(y+1) so that the result is 0 if x = 0.

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.