Function for folding

n = -1:2
x = [2 5 6 8]
[z,v] = flipsig(x,n)
subplot(2,1,1)
stem(n,x)
subplot(2,1,2)
stem(v,z)


function [y,ny] = flipsig(s1, ns)

y = fliplr(s1)
ny = fliplr(-ns)
end