a=input('Type in the left coefficient vector:');
b=input('Type in the right coefficient vector:');
n=input('Type in the range of index n:');
x=input('Type in the expression of input sequence x[n]:');
y=filter(b,a,x);
subplot(2,1,1)
stem(n,x);title('The input sequence x[n]')
subplot(2,1,2)
stem(n,y);title('The output sequence y[n]')