% Script to plot van der Pol phase portrait/sample orbit/Poincare
% map for two values 
%    alpha=0.2 (weakly damped regime, shown in figure(1))
%    alpha = 5 (strongly damped regime, shown in figure(2))

  
  y = -2.5:0.5:2.5;  % y grid used for both alphas

  figure(1)
  clf
  alpha = 0.2;
  z = -2:0.4:2;
  Fmx = 0;
  vanderpol(alpha,y,z,Fmx)
  
  figure(2)
  clf
  alpha = 5;
  z = -10:2:10;
  Fmx = 50;
  vanderpol(alpha,y,z,Fmx)