function X = lynxhare_fn(b,tvec);

% This function numerically evaluates
%
% X(t) = [X1(t);X2(t)]
%
% which satisfies the predator-prey equation.
%
%  dX1/dt =  b(1)*X1 - b(2)*X1*X2
%  dX2/dt = -b(4)*X2 + b(3)*X1*X2
%  X1(0) = b(5), X2(0) = b(6).
% 

tvec = tvec(1:length(tvec)/2);
[tvec,Xsoln] = ode23(@lynxhare_rhs,tvec,[b(5); b(6)],[],b(1:4));
X = Xsoln(:);