matlab常用滤波函数

%the design of butterworth
n=0:0.01:2;
for i=1:4;
     switch i
         case 1;
             N=3;
         case 2;
             N=5;
         case 3;
             N=10;
         case 4;
             N=15;
     end;
     [z,p,k]=buttap(N);%函数调用
     [b,a]=zp2tf(z,p,k);%得到传递函数
     [H,w]=freqs(b,a,n);%特性分析
     magh=abs(H);
     subplot(2,2,i)
     plot(w,magh);
     axis([0 2 0 1]);
     xlabel('w/wc');
     ylabel('|H(jw)|^2');
     title(['butterworth analog filter N=',num2str(N)]);
     grid;end;

契比雪夫I型滤波器

%chebyshev analog lowpass filter
n=0:0.01:2;
for i=1:4;