Package Exports
- @stdlib/math-base-special-factoriallnf
- @stdlib/math-base-special-factoriallnf/dist
- @stdlib/math-base-special-factoriallnf/dist/index.js
- @stdlib/math-base-special-factoriallnf/lib/index.js
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Readme
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factoriallnf
Natural logarithm of the factorial of a single-precision floating-point number.
The natural logarithm of the factorial function may be expressed
The factorial function may be defined as the product
or according to the recurrence relation
Following the convention for an empty product, in all definitions,
The Gamma function extends the factorial function for non-integer values.
The factorial of a negative integer is not defined.
Evaluating the natural logarithm of factorial function is useful as the factorial function can overflow for large n. Thus, factoriallnf( n ) is generally preferred to lnf( n! ).
Installation
npm install @stdlib/math-base-special-factoriallnfUsage
var factoriallnf = require( '@stdlib/math-base-special-factoriallnf' );factoriallnf( x )
Evaluates the natural logarithm of the factorial of a single-precision floating-point number. For input values other than negative integers, the function returns ln( x! ) = ln( Γ(x+1) ), where Γ is the Gamma function. For negative integers, the function returns NaN.
var v = factoriallnf( 3.0 );
// returns ~1.792
v = factoriallnf( 2.4 );
// returns ~1.092
v = factoriallnf( -1.0 );
// returns NaN
v = factoriallnf( -1.5 );
// returns ~1.266If provided NaN, the function returns NaN.
var v = factoriallnf( NaN );
// returns NaNExamples
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var factoriallnf = require( '@stdlib/math-base-special-factoriallnf' );
var opts = {
'dtype': 'float32'
};
var x = uniform( 100, -10.0, 50.0, opts );
logEachMap( 'factoriallnf(%0.4f) = %0.4f', x, factoriallnf );C APIs
Usage
#include "stdlib/math/base/special/factoriallnf.h"stdlib_base_factoriallnf( x )
Evaluates the natural logarithm of the factorial of a single-precision floating-point number. For input values other than negative integers, the function returns ln( x! ) = ln( Γ(x+1) ), where Γ is the Gamma function. For negative integers, the function returns NaN.
float out = stdlib_base_factoriallnf( 3.0f );
// returns ~1.792f
out = stdlib_base_factoriallnf( -1.5f );
// returns ~1.266fThe function accepts the following arguments:
- x:
[in] floatinput value.
float stdlib_base_factoriallnf( const float x );Examples
#include "stdlib/math/base/special/factoriallnf.h"
#include <stdio.h>
int main( void ) {
const float x[] = { 2.0f, 3.0f, 5.0f, 8.0f };
float y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_factoriallnf( x[ i ] );
printf( "factoriallnf(%f) = %f\n", x[ i ], y );
}
}Notice
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For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
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License
See LICENSE.
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