NAME Math::GammaFunction - The Gamma and its related functions SYNOPSIS use Math::GammaFunction qw/:all/; my \$gamma = gamma(5); # 24 my \$fac = faculty(4); # same my \$psi = psi(4); # 1.256... my \$psi_deriv = psi_derivative(\$x, \$order); # order==0 => psi # ... DESCRIPTION This module computes the Gamma function, its logarithmic derivative (the Psi or Digamma function) and the derivatives of the Psi function. It is a thin wrapper around a couple of functions in the math library of the R statistics package. EXPORT None by default. You may choose to export the following functions separately or all at once using the ":all" tag: gamma log_gamma faculty psi psi_derivative SUBROUTINES gamma Takes a real, positive number as argument. Computes the Gamma function. ("n! == Gamma(n+1)") log_gamma Takes a real, positive number as argument. Computes the logarithm of the Gamma function. psi Takes a real as argument. Computes the Psi (or Digamma) function. ("d/dx Gamma(x) == Gamma(x)*Psi(x)" or "d/dx ln(Gamma(x)) == Psi(x)") psi_derivative Takes two arguments: The argument x of the function (real) and the order of the derivative (integer 0 or positive). Computes the n-th derivative of Psi at position x. The maximum derivative is, as far as I can gather from the R sources, 100. This is basically the Polygamma function. faculty Takes a positive integer as argument. Computes its faculty. (Thin wrapper around "gamma") SEE ALSO The actual computation is carried out in C by the excellent R library. Thus, refer to the R manual for details. What I call "gamma" here is the "gammafn" in R's C sources, "log_gamma" is is "gamma" in the C sources. Here's a list of Wikipedia pages about related functions: , , AUTHOR Steffen Mueller, COPYRIGHT AND LICENSE Copyright (C) 2007 by Steffen Mueller This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.6 or, at your option, any later version of Perl 5 you may have available.