log Gamma Frac

Evaluates ln(gamma(b) / gamma(a+b)).

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Interface
LogGammaFrac
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Interface

C++

LogGammaFrac

doublelogGammaFrac(	double	`a`
	double	`b`	)

Given two numbers, divides the gamma function of the 2nd by the gamma function of their sum, then returns the natural logarithm of the quotient:

$ln \left [ \frac{\Gamma(b)}{\Gamma(a+b)} \right ]$

(2)

Example:

#include <codecogs/maths/special/gamma/loggammafrac.h>
#include <stdio.h>
int main()
{
  double a[10] = { 1.6, 1.4, 1.7, 2.0, 1.1, 1.1, 1.2, 1.3, 1.2, 1.5 };
  double b[10] = { 1.2, 2.0, 1.0, 1.2, 1.2, 1.7, 2.0, 1.5, 1.4, 1.5 };
  for( int i=0; i<10; i++ )
    printf( "logGammaFrac( %2.1f, %2.1f ) = %f\n",
            a[i], b[i], Maths::Special::Gamma::logGammaFrac( a[i], b[i] ) );
  return getchar();
}

Output:

logGammaFrac( 1.6, 1.2 ) = -0.602210
logGammaFrac( 1.4, 2.0 ) = -1.092328
logGammaFrac( 1.7, 1.0 ) = -0.435944
logGammaFrac( 2.0, 1.2 ) = -0.970912
logGammaFrac( 1.1, 1.2 ) = -0.239696
logGammaFrac( 1.1, 1.7 ) = -0.612513
logGammaFrac( 1.2, 2.0 ) = -0.885405
logGammaFrac( 1.3, 1.5 ) = -0.637494
logGammaFrac( 1.2, 1.4 ) = -0.477046
logGammaFrac( 1.5, 1.5 ) = -0.813939

Parameters

a	the first number
b	the second number

Authors

Barry W. Brown, James Lovato, Kathy Russell
Updated by Vince Cole (April 2005)

Source Code

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