  N = 70; 
  [D,x] = cheb(N); % cheb.m from Trefethen's "Spectral Methods in MATLAB"
  x = x(2:N); 
  L = 6; x = L*x; D = D/L;                   % rescale to [-L,L]
  A = -D^2; A = A(2:N,2:N) + (1+3i)*diag(x.^2);
  opts.npts=50;
  opts.ax = [0 50 0 40];
  opts.levels = -10:.5:0;
  opts.proj_lev = .7;
  eigtool(A,opts)
