% This function defines the system dynamics for "sfbdir_ex1"

function [y] = extdisc_ex3sys(t, x, flag, SysData, fcnflag)

n = SysData.n;

% Strip out the plant states
xi = x(1:n); xi = xi(:);
dxi = zeros(n, 1);     % pre-allocate

switch (fcnflag)
case 'deriv'

  % Define the plant dynamics
  dxi(1) = xi(2); 
  dxi(2) = 2*xi(1) - 0.1*(xi(1))^3;

  y = [dxi];

case 'output'
  
  y = [xi(1); xi(2)];
end