function q = lp_orders(e, n)
% LP_ORDERS  Observed convergence order between successive refinements.
%
% q(k) = log(e(k-1)/e(k)) / log(n(k)/n(k-1)), and NaN wherever the ratio is not
% a positive finite number — an error of exactly zero, or a resolution a method
% skipped, would otherwise put an Inf or a complex value in the table.
q = NaN(size(e));
for k = 2:numel(e)
    r = e(k-1) / e(k);
    if isfinite(r) && r > 0
        q(k) = log(r) / log(n(k) / n(k-1));
    end
end
end