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/