weka.core
Class SpecialFunctions

java.lang.Object
  weka.core.SpecialFunctions

public final class SpecialFunctions
extends java.lang.Object

Class implementing some mathematical functions.

Version:

$Revision: 1.1 $

Author:

Eibe Frank ([email protected])

Constructor Summary

SpecialFunctions()

Method Summary

static double	lnFactorial(double x) Returns natural logarithm of factorial using gamma function.
static double	lnGamma(double x) Returns natural logarithm of gamma function.
static double	log2Binomial(double a, double b) Returns base 2 logarithm of binomial coefficient using gamma function.
static double	log2Multinomial(double a, double[] bs) Returns base 2 logarithm of multinomial using gamma function.
static void	main(java.lang.String[] ops) Main method for testing this class.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SpecialFunctions

public SpecialFunctions()

Method Detail

lnFactorial

public static double lnFactorial(double x)

Returns natural logarithm of factorial using gamma function.

Parameters:

x - the value

Returns:

natural logarithm of factorial

lnGamma

public static double lnGamma(double x)

Returns natural logarithm of gamma function. Converted to java from Numerical Recipes in C.

Parameters:

x - the value

Returns:

natural logarithm of gamma function

log2Binomial

public static double log2Binomial(double a,
                                  double b)
                           throws java.lang.ArithmeticException

Returns base 2 logarithm of binomial coefficient using gamma function.

Parameters:

a - upper part of binomial coefficient

b - lower part

Returns:

the base 2 logarithm of the binominal coefficient a over b

Throws:

java.lang.ArithmeticException

log2Multinomial

public static double log2Multinomial(double a,
                                     double[] bs)
                              throws java.lang.ArithmeticException

Returns base 2 logarithm of multinomial using gamma function.

Parameters:

a - upper part of multinomial coefficient

bs - lower part

Returns:

multinomial coefficient of a over the bs

Throws:

java.lang.ArithmeticException

main

public static void main(java.lang.String[] ops)

Main method for testing this class.