gram

% -*- texinfo -*-
% @deftypefn {Function File} {@var{W} =} gram (@var{sys}, @var{mode})
% @deftypefnx {Function File} {@var{Wc} =} gram (@var{a}, @var{b})
% @code{gram (@var{sys}, 'c')} returns the controllability gramian of
% the (continuous- or discrete-time) system @var{sys}.
% @code{gram (@var{sys}, 'o')} returns the observability gramian of the
% (continuous- or discrete-time) system @var{sys}.
% @code{gram (@var{a}, @var{b})} returns the controllability gramian
% @var{Wc} of the continuous-time system @math{dx/dt = a x + b u};
% i.e., @var{Wc} satisfies @math{a Wc + m Wc' + b b' = 0}.
%
% @end deftypefn