factorial
Factorial, Combinations, and Permutations

### Description

Computes the factorial (n!), the binomial coefficients, and the number of combinations.

### Usage

    factorial(x)
    lfactorial(x)
    choose(n, k)
    lchoose(n, k)

### Arguments

x, n | an integer vector. Need not to be an integer for factorial or lfactorial.
k | an integer vector.
m | an integer vector that sums to n.

### Details

These functions use gamma and lgamma for computations.
Value
returns a numeric vector. Specifically:

factorial(x) | returns x!.
lfactorial(x) | returns the natural logarithm of x!.
choose(n, k) | returns n! / (k! (n-k)!); the number of ways of selecting k items from n when order does not matter.
lchoose(n, k) | returns the natural logarithm of n! / (k! (n-k)!).

See Also
gamma, lgamma
Examples

    factorial(5:7)
    lfactorial(5.5)
    choose(5, 2)
    lchoose(5.2, 2)
    choose(5, -1:6)

Package base version 6.1.5-18
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