用matlab设计巴特沃斯IIR数字低通滤波器对其进行信号处理(要matlab程序)

Wp=0.2;Ws=0.3;Ap=1;As=15; [N,wc]=buttord(Wp,Ws,Ap,As); [b,a]=butter(N,wc); xn=[-4,-2,0,-4,-6,-4,-2,-4,-6,-6,-4,-4,-6,-6,-2,6,12,8,0,-16,-38,-60,-84,-90,-66,-32,-4,-2,-4,8,12,12,10,6,6,6,4,0,0,0,0,0,-2,-4,0,0,0,-2,-2,0,0,-2,-2,-2,-2,0]; yn=filter(b,a,x