% p25.m - stability regions for ODE formulas

% Backward differentiation:
  clf
  z = exp(1i*pi*(0:200)/100); r = z-1;
  d = 1-1./z;
  plot([-40 40],[0 0]), hold on, plot([0 0],[-40 40]) 
  r = 0; for i = 1:6, r = r+(d.^i)/i; plot(r), end   % orders 1-6
  axis([-15 35 -25 25]), axis square, grid on
  title('backward differentiation')
