Evaluate the natural logarithm of a double-precision floating-point number.
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> Evaluate the [natural logarithm][natural-logarithm] of a double-precision floating-point number.
``bash`
npm install @stdlib/math-base-special-ln
`javascript`
var ln = require( '@stdlib/math-base-special-ln' );
#### ln( x )
Evaluates the [natural logarithm][natural-logarithm] of a double-precision floating-point number.
`javascript
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][natural-logarithm] is not defined.
`javascript`
var v = ln( -4.0 );
// returns NaN
`javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var ln = require( '@stdlib/math-base-special-ln' );
var opts = {
'dtype': 'float64'
};
var x = discreteUniform( 100, 0, 100, opts );
logEachMap( 'ln(%0.4f) = %0.4f', x, ln );
`
*
`c`
#include "stdlib/math/base/special/ln.h"
#### stdlib_base_ln( x )
Evaluates the [natural logarithm][natural-logarithm] of a double-precision floating-point number.
`c`
double v = stdlib_base_ln( 2.0 );
// returns ~0.693
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_ln( const double x );
`c
#include "stdlib/math/base/special/ln.h"
#include
#include
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 );
}
}
`
*
- [@stdlib/math-base/special/exp][@stdlib/math/base/special/exp]: natural exponential function.
- [@stdlib/math-base/special/log10][@stdlib/math/base/special/log10]: common logarithm (base ten).
- [@stdlib/math-base/special/log1p][@stdlib/math/base/special/log1p]: evaluate the natural logarithm of 1+x.
- [@stdlib/math-base/special/log2][@stdlib/math/base/special/log2]: binary logarithm (base 2).
*
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
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---
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[natural-logarithm]: https://en.wikipedia.org/wiki/Natural_logarithm
[@stdlib/math/base/special/exp]: https://www.npmjs.com/package/@stdlib/math-base-special-exp
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