# Solve and plot the phase portrait for van der pol ODE with time dependent term

19 views (last 30 days)
F.O on 27 Mar 2019
Commented: Rena Berman on 2 Apr 2019
I want to solve this system of ode by ode45 and then plot the x1 and x2 with t and phase portrait later but I got error which i couldint figure out
How i could draw the vector field and eigen vectors in the phase portrait because i dont get by using ode set and odephase 2
function [dxdt] = myode(t,x,gt,g,lambda,gamma,omega)
g=interp1(gt,g,t)
dxdt=zeros(2,1);
dxdt(1)=x(2);
dxdt(2)=lambda.*(1-x(1)^2)*x(2)-x(1)+g;
end
%script
gamma=0.25;
omega=[1.04 1.1];
gt=[0 ,500]
g=gamma.*sin(omega(1).*gt)
% g=gamma.*sin(omega(2).*gt)
lambda=0.01;
x0=[1 0]
tspan=[0 500];
opts = odeset('RelTol',1e-2,'AbsTol',1e-4);
[t2,x2]=ode45(@(t,x) myode(t,x,gt,g,gt,lambda,gamma,omega(1)),tspan,x0,opts);
% ploting the phase portait
function PLOT_VDP()
figure(1)
options=odeset('OutputFcn', @odephas2);
lambda=0.01;
gamma=0.25;
omega=[1.04 1.1];
x0=[1; 0]
x01=[3;0]
tspan=[0 500];
[t,x]=ode45(@(t,x) myode(t,x,g,lambda,gamma,omega(1)),tspan,x0,options);
end
Rena Berman on 2 Apr 2019

madhan ravi on 27 Mar 2019
Edited: madhan ravi on 27 Mar 2019
g,lambda
%^—-missed it
Don’t name variable lambda (will shadow in-built function gamma())
madhan ravi on 27 Mar 2019
Edited: madhan ravi on 27 Mar 2019
After someone answers the question it’s not appropriate to edit the question!! You have some problems with declaring the input arguments while calling the function, analyse slowly and observe what obvious mistake you made.

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