% Example 5 of D.R. Wille' and C.T.H. Baker, DELSOL--a numerical code for the
% solution of systems of delay-differential equations, Appl. Numer. Math., 9
% (1992) 223-234. This is an example of a scalar equation that exhibits chaotic
% behavior. Equation (7) of the paper includes a parameter gamma, but no value
% is specified in the example. A value of -1 gives qualitative agreement with
% Fig. 3 of the paper. The length of the interval of integration is also not
% given. Here an interval [0, 100] is used; it is clearly shorter than that of
% the figure, but the qualitative behavior is seen already.
sol = dde23('exam2f',2,0.5,[0, 100]);
t = linspace(2,100,1000);
y = ddeval(sol,t);
ylag = ddeval(sol,t - 2);
plot(y,ylag)
title('Figure 2. Example 5 of Wille'' and Baker.')
xlabel('y(t)');
ylabel('y(t-2)');
axis([0 1.5 0 1.5])