f=@(x,y) cos(x);
% Calculate exact solution
g=@(x) cos(x);
xe=(0:.1:100);
ye=g(xe);
% Call function
[x4,y4]=ode45(f,[0,100],.1);
% Plot
plot(xe,ye,'k-',x4,y4,'o')
xlabel('x')
ylabel('y')
legend('Analytical','ode45')
axis([0 10 100 100])