function sys_c=d2c(sys_d,varargin)
% Discrete time systems should not be converted to continuous ones!

% sys_c=d2c(sys_d,...)
%
% Converts discrete-time system to continuous-time system. See ss/d2c
% for optimal arguments.

warning(['Discrete time systems should not be converted to continuous ones! Do it anyway.']);

if sys_d.Ts ~= 0
    Ts=sys_d.Ts;
    % convert ss part
    sys_c=d2c(ss(sys_d),varargin{:});
    % convert noise part
    sys_c=ess(sys_c,sys_d.l,sys_d.q/Ts,sys_d.r*Ts,sys_d.m);
else
    warning('Discrete system must be given');
    sys_c = sys_d;
end