edu.northwestern.at.utils.math

Class Factorial

java.lang.Object

edu.northwestern.at.utils.math.Factorial

public class Factorial
extends java.lang.Object

Defines methods for factorials.

Field Summary

Fields

Modifier and Type	Field and Description
protected static double[]	doubleFactorials
protected static long[]	longFactorials

Constructor Summary

Constructors

Constructor and Description
Factorial()

Method Summary

Methods

Modifier and Type	Method and Description
static double	factorial(int n) Compute factorial of an integer.
static double	logFactorial(int n) Computes the natural log of n factorial.

Methods inherited from class java.lang.Object

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

Field Detail

longFactorials

protected static final long[] longFactorials

doubleFactorials

protected static final double[] doubleFactorials

Constructor Detail

Factorial

public Factorial()

Method Detail

factorial

public static double factorial(int n)

Compute factorial of an integer.

Parameters:

n - Number for which to compute factorial.

Returns:

n!

logFactorial

public static double logFactorial(int n)

Computes the natural log of n factorial.

Parameters:

n - The number for which the log factorial is desired.

Returns:

The natural log of n! .

We use the LogGamma function to compute log(n!) using the relation:

log(n!) = logGamma( n + 1 )