%program p316
F = [0 0.3  0.4 0.6  0.7 0.9]; 
A = [0  1   0  0  0.5 0.5];
b = remez(24,F,A);
for i=1:2:6, 
   plot([F(i) F(i+1)],[A(i) A(i+1)],'--'), hold on
end
[H,f] = freqz(b,1,512,2);
plot(f,abs(H)), grid on, hold off
axis([0 1 0 1]);
legend('Ideal','firls Design')