function dXdt=rps1(t,X)
  x=X(1);
y=X(2);
a=1.2;
b=.8;
z=1-x-y;
fx=-a*y+b*z;
fy=b*x-a*z;
fz=b*y-a*x;
phi=fx*x+fy*y+fz*z;
xp=x*(fx-phi);
yp=y*(fy-phi);
dXdt=[xp;yp];
% in matlab, type [t,X]=ode23(@rps1,[0,200],[.3,.32]);
% and then plot(X(:,1),X(:,2)) to get the x-y phaseplane
  % NOTE the last [.3,.32] is initial data

