function [db,mag,pha,grd,w] = freqz_m(b,a);[H,w] = freqz(b,a,1000,'whole');H = (H(1:1:501))'; w = (w(1:1:501))';mag = abs(H);db = 20*log10((mag+eps)/max(mag));pha = angle(H);grd = grpdelay(b,a,w);