Hi,

given the following:

. mat i = (1, 2, 3)

. mat lis i

i[1,3]
c1 c2 c3
r1 1 2 3

.
. mat N = i' * i

. mat lis N

symmetric N[3,3]
c1 c2 c3
c1 1
c2 2 4
c3 3 6 9

... hot to create matrix in which instead of products I would have differences:
c1 c2 c3
c1 0
c2 1 0
c3 2 1 0