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

Methods
Modifier and Type Method and Description
`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)