I have benefited greatly from the members in the XSL/Saxon communities, and I would like to contribute myself.
I have recently worked up a primitive collection of functions designed to allow XSL to do vector analysis and linear algebra. It handles things like finding projections onto linear subspaces, cofactors, adjoints, determinants, and minors. It can also invert matrices and solve systems.
I have in conjunction written up an implementation of a solver for doing robust non-linear regression for a data set. Notably, some dedicated statistical analysis software (e.g., R) does not have this capability.