This Perl package exports functions for performing numerical first
(Derivative1) and second Derivative2) order differentiation on vectors
of data. They both take references to two arrays containing the x and y
ordinates of the data and return an array of the 1st or 2nd derivative
at the given x ordinates. Derivative2 may optionally be given values to
use for the first dervivative at the start and end points of the data -
otherwiswe 'natural' values are used.

WWW: http://search.cpan.org/dist/Math-Derivative/