Factorial of large numbers

This function implements a standard algorithm for computing factorials. It may not be the most efficient for very large arguments, but it is very transparent. The function accepts single numbers as inputs or arrays.

Note that for any real work, the code suggested by John D'Errico is actually preferable, because it is faster and more precise. This code is implemented in another file on FEX, logfactorial. I would therefore suggest that you use that function instead of largefactorial.