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## weka.core
Class SpecialFunctions

    java.lang.Object
      weka.core.SpecialFunctions

All Implemented Interfaces:
  RevisionHandler

    public final class SpecialFunctions

extends java.lang.Object
implements RevisionHandler

Class implementing some mathematical functions.

Version:
  $Revision: 1.8 $
Author:
  Eibe Frank (eibe@cs.waikato.ac.nz)

Constructor Summary
`SpecialFunctions()`

Method Summary
`java.lang.String` | `getRevision()` Returns the revision string.
`static double` | `lnFactorial(double x)` Returns natural logarithm of factorial using 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

### log2Binomial

    public static double log2Binomial(double a,
                                      double b)

  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

### log2Multinomial

    public static double log2Multinomial(double a,
                                         double[] bs)

  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

### getRevision

    public java.lang.String getRevision()

  Returns the revision string.

  Specified by:
    `getRevision` in interface `RevisionHandler`
  Returns:
    the revision

### main

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

  Main method for testing this class.

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