function[x,n]=xlpy(x1,n1,n0)
n=n1+n0;x=x1;
xlabel('n')
axis([min(n)-1,max(n)+1,min(x)-0.5,max(x)+0.5])

x=[3,3,3,3,2,0,1];
n=-3:3;
[x1,n1]=xlpy(x,n,4)
[x2,n2]=xlpy(x,n,-2)
n=min([n1,n2]):max([n1,n2])
N=max([n1,n2])-min([n1,n2])
y1=zeros(1,N)
y2=zeros(1,N)
y1(find(n>=min(n1)&n<max(n1)))=x1
y2(find(n>=min(n2)&n<max(n2)))=x2
y=y1.*y2
stem(n,y,'filled');
title('x(n-4)x(n+2)')
请问一下大家这个程序哪里有问题呢
显示是一张空白图表