%%% Nonlinear Systems Analysis, NTU-EE, 91 Fall
%%% Phase Portrait of Van der Pol oscillator
%%% Date: Sep. 26, 2002
%%% By Feng-Li Lian, fengli@ntu.edu

close all; clear all

xinit = [
 [(0:0.5:3) (0:0.5:3) -(0:0.5:3) -(0:0.5:3)]'  [(0:0.5:3) -(0:0.5:3) (0:0.5:3) -(0:0.5:3)]' ];

figure(11)
  plot( xinit(:,1), xinit(:,2), 'rx' ); hold on
    
for i = 1:28
  [ t, x ] = ode45( @funVanderPol, [ 0 20 ], xinit(i,:));   
 
  figure(11)
  plot( x(:,1), x(:,2), '-' );
end