% rungederiv.m
% routine to plot derivatives of Runge's example, f(x) = 1/(1+x^2) on [-5,5]
 figure(1), clf, set(gca,'fontsize',18)
 for j=0:25
    syms x
    fj = vectorize(diff(1/(x^2+1),j));             % compute derivative (symbolic toolbox)
    x = linspace(-5,5,1000); fjx = eval(fj);       % evaluate on a grid of points
    plot(x,fjx,'b-','linewidth',2);                % plot derivative
    title(sprintf('Runge''s Example: f^{(%d)}(x)',j),'fontsize',14)
    input(' ')
  end