% -*- texinfo -*-
% @deftypefn {Function File} {} ctrb (@var{sys}, @var{b})
% @deftypefnx {Function File} {} ctrb (@var{a}, @var{b})
% Build controllability matrix:
% @iftex
% @tex
% $$ Q_s = [ B AB A^2B \ldots A^{n-1}B ] $$
% @end tex
% @end iftex
% @ifinfo
% @example
% 2 n-1
% Qs = [ B AB A B ... A B ]
% @end example
% @end ifinfo
%
% of a system data structure or the pair (@var{a}, @var{b}).
%
% @command{ctrb} forms the controllability matrix.
% The numerical properties of @command{is_controllable}
% are much better for controllability tests.
% @end deftypefn