function [yend t y] =  shooting(l, q, b)
% solves -y'' = l.q(x).y

F = @(x,y) [y(2); -l*q(x)*y(1)];
[t y] = ode45(F, [0 b], [0;1], odeset('reltol', 1e-9)); % launch y=0, y'=1
yend = y(end,1);    % extract just final value
