Coupled ODE Solver Producing Unexpected Graph

Incorrect graph generating with given code. Trying to solve a couped ODE problem. Thank you in advance.
clear;
clc;
t_initial=0;
t_final=800;
x0=500;
y0=200;
tSpan=[t_initial t_final];
v0=[x0 y0];
[t,v]=ode45(@ODEfun,tSpan,v0);
figure
plot(t,v(:,1),t,v(:,2));
legend('Fox','Rabbit');
xlabel('Time (days)');
ylabel('Population');
title('Rabbit and Fox Population Overtime');
function f=ODEfun(~,v)
x=v(1);
y=v(2);
k1=0.02;
k2=0.0004;
k3=0.00004;
k4=0.04;
dx_dt=(k1*x)-(k2*y);
dy_dt=(k3*x*y)-(k4*y);
f=[dx_dt;dy_dt];
end

2 个评论

Here is what i got for t_final = 80
img1.png
I think you seem to get correct graph only for the given input conditions
Do you mean a graph like this below ?

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R2018a

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