org.apache.commons.numbers.combinatorics

Class LogBinomialCoefficient

java.lang.Object

org.apache.commons.numbers.combinatorics.LogBinomialCoefficient

public class LogBinomialCoefficient
extends Object

Natural logarithm of the binomial coefficient. It is "n choose k", the number of k-element subsets that can be selected from an n-element set.

Constructor Summary

Constructors

Constructor and Description
LogBinomialCoefficient()

Method Summary

Modifier and Type	Method and Description
static double	value(int n, int k) Computes the logarithm of the binomial coefficient.

Methods inherited from class java.lang.Object

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

Constructor Detail

LogBinomialCoefficient

public LogBinomialCoefficient()

Method Detail

value

public static double value(int n,
                           int k)

Computes the logarithm of the binomial coefficient. The largest value of n for which all coefficients can fit into a long is 66.

Parameters:

n - Size of the set.

k - Size of the subsets to be counted.

Returns:

log(n choose k).

Throws:

IllegalArgumentException - if n < 0.

IllegalArgumentException - if k > n.

IllegalArgumentException - if the result is too large to be represented by a long.