function ode1(F, tspan, y0, h)
% ODE1 : demo version of simple Euler method
% ode1(F, tspan, y0, h) uses step size h and plots 1D results


t0 = tspan(1);
tfinal = tspan(2);

t = t0;
y = y0;
plot(t,y,'r.');
hold on
while t <= tfinal
    y = y + h*feval(F,t,y);
    t = t + h;
    plot(t,y,'r.')
end;
hold off;