 ; F = factorize(A) ; x = F\b ; y = F\c ; toc

%% Underdetermined systems
%
% The under-determined system A*x=b where A has more columns than rows has
% many solutions.  x=A\b finds a basic solution (some of the entries in x
% are zero).  pinv(A)*b finds a minimum 2-norm solution, but it's slow.  QR
% factorization will do the same if A has full rank.  That's what the
% factorize(A) and inverse(A) methods do.

A = rand (200,1000) ;
b = rand (200,1) ;

tic ; x = A\b            ; toc, norm (x)
tic ; x = pinv(