% The following 3 lines produce filter coefficients shown in Table 6.1.
wp = [0.35,0.65]; ws = [0.25,0.75]; Rp = 1; As = 50;
[N, wn] = ellipord(wp, ws, Rp, As);
[b,a] = ellip(N,Rp,As,wn);
w = [0:500]*pi/500; H = freqz(b,a,w); magH = abs(H);
magHdb = 20*log10(magH);
.....