c76.m

matlab例程MATLAB 6.x版的内建数据类型（Built-in data type）就有5种以上

Wp=10;Ws=20;Gp=-2;Gs=-20;
[n,Wc]=buttord(Wp,Ws,-Gp,-Gs,'s');
[num,den]=butter(n,Wc,'s')
w=0:.01:40; w=w';
[mag,phase,w]=bode(num,den,w);
plot(w,mag)