factorial(x), x REAL |

factorial(x) computes x! (x factorial), where x is a REAL scalar, vector, matrix or array. The result is the same size and shape as as x. If any element is MISSING, <= -1 or such that x! is too large to be computed, the corresponding element of the result is MISSING. Elements of x need not be integers. x! is computed as exp(lgamma(x+1)), except that if x is an integer <= 20 the value should be exact. See also binom() and lgamma().

Gary Oehlert 2003-01-15