How to draw the direction field of van der pol oscillator?

Question

Gopichandh Danala 2017-3-23

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/331449-how-to-draw-the-direction-field-of-van-der-pol-oscillator

回答： KSSV 2017-3-23

mu1.jpg

在 MATLAB Online 中打开

Hi, I am trying to get the direction field and phase portrait shown on this wiki page:

https://en.wikipedia.org/wiki/Van_der_Pol_oscillator

My code:

options = odeset('MaxStep',0.5);
temp = inputdlg('Enter mu value');
mu = str2double(temp{1,1});
[t,y] = ode45(@(t,y) vdp1_1(t,y,mu),[0 10],[2; 0],options);
figure(1);
plot(t,y(:,1)), 
xlabel('time t');
ylabel('Y1(t)');
title('t vs Y1(t)');
figure(2);
plot(t,y(:,2))
xlabel('time t');
ylabel('Y2(t)');
title('t vs Y2(t)');
figure(3),
 plot(y(:,1),y(:,2)) , hold on
quiver(y(:,1), y(:,2), gradient(y(:,1)), gradient(y(:,2) ))
hold off
function dydt = vdp1_1(t,y,mu)
dydt = zeros(2,1);
dydt(1) = y(2);
dydt(2) = [mu * (1-y(1)^2)*y(2)-y(1)];
end