ex07ch4.m

these codes are for solving OED with matlab

function sol = ex07ch4
options = ddeset('InitialY',[0; 0],'AbsTol',1e-9);
sol = dde23(@ddes,[1, 2],@history,[0, 4],options);
plot(sol.x,sol.y);
%=================================================
function dydt = ddes(t,y,Z)
ylag1 = Z(:,1);
ylag2 = Z(:,2);
dydt = [ ylag1(1)*ylag2(2); -y(1)*ylag2(2)];

function v = history(t)
v = [cos(t); sin(t)];