function qdot=diffeq(t,q)

% a scalar example
qdot=cos(t);

% % an example with three states
% m=1000; k=10000; b=3000;
% 
% A=[0 1 0;
%     -k/m -b/m k/m ;
%     0 0 0];
% B = [0 b/m 1]';
% 
% u = 0.2*pi*cos(2*pi*t);
% 
% qdot = A*q + B*u;