is_observable

% -*- texinfo -*-
% @deftypefn {Function File} {[@var{retval}, @var{u}] =} is_observable (@var{a}, @var{c}, @var{tol})
% @deftypefnx {Function File} {[@var{retval}, @var{u}] =} is_observable (@var{sys}, @var{tol})
% Logical check for system observability.
%
% Default: tol = @code{tol = 10*norm(a,'fro')*eps}
%
% Returns 1 if the system @var{sys} or the pair (@var{a}, @var{c}) is
% observable, 0 if not.
%
% See @command{is_controllable} for detailed description of arguments
% and default values.
% @seealso{size, rows, columns, length, ismatrix, isscalar, isvector}
% @end deftypefn