MATLAB: Lotka-volterra with ode45

lotka volterra ode45

I have the following system of differential equations:

P' = P − 0.05PR

R' = −0.5R + 0.02PR

My function is the following one:

function xdot = Lotka(t,x)
xdot = [x(1) - 0.05*x(1)*x(2); -0.5*x(2)-0.02*x(1)*x(2)];

To find the solution i use ode45:

[t,x] = ode45(@Lotka, [0 20],[10 10]);
plot(t,x(:,1));
hold on
plot(t,x(:,2));

But Matlab is still running… No error is given… It just keeps running. What went wrong?

Best Answer

Problem may be stiff. Try ode15s instead.

Related Solutions

MATLAB: Lotka-Volterra Predatir Prey Model Code

using this:

function [dPdt] = lotkavolterra(t,P)
alpha = 1.5; % you have error here: you using alpa
beta = 1;
gamma = 3;
delta = 1;
x = P(1);
y = P(2);
dPdt = zeros(2,1);
dPdt(1) = alpha*x - beta*x*y;
dPdt(2) = delta*x*y - gamma*y;
end

MATLAB: Anonymous function in ode45: column vector error

You are not calling ‘xdot’ correctly in your ode45 call.

Try this:

t = 0:.01:20;
x0 = [0 0]' + eps;
xdot = @(t,x) [0 1; 0 0] * x;
[T,X] = ode45(xdot,t,x0)
figure
plot(T, X)
grid

Also, the result is uniformly zero, so to prevent that, I added eps to ‘x0’.

Best Answer

Related Solutions

MATLAB: Lotka-Volterra Predatir Prey Model Code

MATLAB: Anonymous function in ode45: column vector error

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