function dy = SimpleEGTDEs(t,y,p)
%   ======================
%   Simple evolutionary game theory differential equations
%   2013 August 5
%   ======================

T = p(1);
R = p(2);
P = p(3);
S = p(4);

f1 = y(1)/sum(y);
f2 = y(2)/sum(y);

dy = zeros(2,1);
dy(1) = (R*f1 + S*f2)*y(1);
dy(2) = (T*f1 + P*f2)*y(2);