function ydot = lotka(t, y)
% LOTKA :  function to be integrated to solve an ODE
%
% ydot = lotka(t, y)
%        t is a scalar time
%        y is a vector of variables
%        ydot is the vector dy/dt
%
% Lotka-Volterra equations
%
% y = [rabbits(t); foxes(t)]

alpha = .01;

ydot = [2*y(1) - alpha * y(1) * y(2);   ...
        -y(2)  + alpha * y(1) * y(2)];