function predator

x0 = 200;         % initial number of rabbits
y0 = 10;        % initial number of foxes
T = 300;        % final time

options = odeset('RelTol',1e-4,'AbsTol',[1e-4 1e-4]);
[t,z] = ode45(@preprey,[0 T],[x0 y0],options);

plot(t,z(:,1),'b',t,z(:,2),'r')


function dz = preprey(t,z)

a = .04;
b = .0002;
c = .08;
d = .0004;

x = z(1);
y = z(2);

dz = zeros(2,1);

dz(1) = a*x - b*x*y;
dz(2) = -c*y + d*x*y;