m=[1];
mtilde=[1];
ell=[1 1];
elltilde=[1 1];

figure(1)
xlabel('Real')
ylabel('Imaginary')
for alpha=0:0.05:10
   [X,E]=bp4eig( m, mtilde, ell, elltilde, alpha ); 
   E=diag(E);
   plot(real(E),imag(E),'o','MarkerSize',2);
   xlim([-4,0.5]);
   hold on;
   pause(0.1);
end
hold off