org.opensourcephysics.numerics.specialfunctions
Class Factorials

java.lang.Object
  org.opensourcephysics.numerics.specialfunctions.Factorials

public class Factorials
extends java.lang.Object

Computes the factorial of an integer and functions closely related to factorials.

Method Summary

static double	factorial(int n) Calculates the factorial.
static double	gammaln(double x) Calculates the logarithm of the Gamma function using the Lanczos approximation.
static double	logChoose(int n, int k) Returns the logarithm of the binomial coefficient (n, k) In other notation: log (n choose k) (n choose k) represents the number of ways of picking k unordered outcomes from n possibilities
static double	logFactorial(int n) Returns log (n!) = log (n * (n-1) * ...
static double	poisson(double nu, int n) Returns the Poisson distribution (nu^n e^(-nu) / n!)

Methods inherited from class java.lang.Object

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

Method Detail

gammaln

public static double gammaln(double x)

Calculates the logarithm of the Gamma function using the Lanczos approximation.

Parameters:

x - double

Returns:

double

factorial

public static double factorial(int n)

Calculates the factorial.

Parameters:

n - int

Returns:

double

logFactorial

public static double logFactorial(int n)

Returns log (n!) = log (n * (n-1) * ... 2 * 1)

Parameters:

n -

Returns:

log(n!)

poisson

public static double poisson(double nu,
                             int n)

Returns the Poisson distribution (nu^n e^(-nu) / n!)

Parameters:

nu -

n -

Returns:

poisson_nu(n)

logChoose

public static double logChoose(int n,
                               int k)

Returns the logarithm of the binomial coefficient (n, k) In other notation: log (n choose k) (n choose k) represents the number of ways of picking k unordered outcomes from n possibilities

Parameters:

n -

k -

Returns:

log (n choose k)