% -*- texinfo -*-
% @deftypefn {Function File} {[@var{a}, @var{b}, @var{c}, @var{d}] =} tf2ss (@var{num}, @var{den})
% Conversion from transfer function to state-space.
% The state space system:
% @iftex
% @tex
% $$ \dot x = Ax + Bu $$
% $$ y = Cx + Du $$
% @end tex
% @end iftex
% @ifinfo
% @example
% .
% x = Ax + Bu
% y = Cx + Du
% @end example
% @end ifinfo
% is obtained from a transfer function:
% @iftex
% @tex
% $$ G(s) = { { \rm num }(s) \over { \rm den }(s) } $$
% @end tex
% @end iftex
% @ifinfo
% @example
% num(s)
% G(s)=-------
% den(s)
% @end example
% @end ifinfo
%
% The vector @var{den} must contain only one row, whereas the vector
% @var{num} may contain as many rows as there are outputs @var{y} of
% the system. The state space system matrices obtained from this function
% will be in controllable canonical form as described in @cite{Modern Control
% Theory}, (Brogan, 1991).
% @end deftypefn