Matlab——filter函数用法

y = filter(b,a,X)
[y,zf] = filter(b,a,X)
[y,zf] = filter(b,a,X,zi)
y = filter(b,a,X,zi,dim)
[...] = filter(b,a,X,[],dim)

clc;
clear;
n = 0:100;
x1 = exp(1i*(pi/4)*n);
a = [1 0.9];
b = [1 -0.25];
y1 = filter(a,b,x1);
stem(n,real(y1));
hold;
stem(n,imag(y1));
xlabel('n');
ylabel('y1');