c712.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

%bandpass filter

Wp=[1000 2000];
Ws=[450 4000];
Gp=-2.4;Gs=-20;


% Butter 
[N,Wn]=buttord(Wp,Ws,-Gp,-Gs,'s')
[num,den]=butter(N,Wn,'s')


% Cheby1
%[N,Wn]=cheb1ord(Wp,Ws,-Gp,-Gs,'s');
%[num,den]=cheby1(N,-Gp,Wn,'s')

% Cheby2
%[n,Ws]=cheb2ord(Wp,Ws,-Gp,-Gs,'s');
%[num,den]=cheby2(n,-Gs,Ws,'s')

% Elliptic filter

%[n,Wn]=ellipord(Wp,Ws,-Gp,-Gs,'s');
%[num,den]=ellip(n,-Gp,-Gs,Wn,'s')



w=0:1:10^4; w=w';
[mag,phase,w]=bode(num,den,w);
plot(w,mag)