 inverse (A) ; S (2:3,4), toc

%% Computing the entire inverse or pseudo-inverse
%
% Rarely, and I mean RARELY, you really do need the inverse.  More
% frequently what you want is the pseudo-inverse.  You can force a
% factorization to become a plain matrix by converting it to double.  Note
% that inverse(A) only handles full-rank matrices (either dense or
% sparse), whereas pinv(A) works for all dense matrices (not sparse).
%
% The explicit need for inv(A) (or S=A\eye(n), which is the same thing) is
% RARE