Binary Logarithm

Evaluate the binary logarithm.

The binary logarithm (logarithm with base 2) is defined for any positive real number as

Installation

npm install @stdlib/math-base-special-log2

Usage

var log2 = require( '@stdlib/math-base-special-log2' );

log2( x )

Evaluates the binary logarithm.

var v = log2( 4.0 );
// returns 2.0

v = log2( 0.0 );
// returns -Infinity

v = log2( Infinity );
// returns Infinity

v = log2( NaN );
// returns NaN

For negative numbers, the binary logarithm is not defined.

var v = log2( -4.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var log2 = require( '@stdlib/math-base-special-log2' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = round( randu() * 100.0 );
    console.log( 'log2(%d) = %d', x, log2( x ) );
}

C APIs

Usage

#include "stdlib/math/base/special/log2.h"

stdlib_base_log2( x )

Evaluates the binary logarithm.

double out = stdlib_base_log2( 4.0 );
// returns 2.0

The function accepts the following arguments:

• x: [in] double input value.

double stdlib_base_log2( const double x );

Examples

#include "stdlib/math/base/special/log2.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 ) * 100.0 );
        v = stdlib_base_log( x );
        printf( "log2(%lf) = %lf\n", x, v );
    }
}

See Also

• @stdlib/math-base/special/exp2: base 2 exponential function.
• @stdlib/math-base/special/ln: evaluate the natural logarithm of a double-precision floating-point number.
• @stdlib/math-base/special/log: base b logarithm.

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

Copyright

Copyright © 2016-2024. The Stdlib Authors.