fs = 10;
tspan = [0:1/fs:100]; % specify the time points
xint = [3.0;2.0;1.0];
[t,x]= ode45(@nonlin,tspan,xint);
% remove some trainsition part of x
t = t(100:end);
x = x(100:end, :);
subplot(211); plot(t, x)
subplot(212); plot(20*log10(abs(fft(x))))
function dxdt = nonlin(t,x)
e = 2.5;
dxdt = zeros(3,1);
dxdt(1) = -(x(2)+x(3));
dxdt(2) = x(1) + ((1/5)*x(2));
dxdt(3) = (1/5)+(((x(1)-e))*x(3));
end
