Afraid you're over my head -I'm an accountant/auditor. Maybe some actual
numbers would help. This is a bit of a guess based on trying to interpret
your original formula, so please provide a correct example if none of it
helps you.

If, in A1:A3, you have

1
2
8

are you trying to get:

11 (SUM(1*1, 1*2, 1*8))
22 (SUM(2*1, 2*2, 2*8))
88 (SUM(8*1, 8*2, 8*8))

which would be =SUM(A$1:A$3)*A1 (enter it in a single cell, then copy the
formula down and across - the column references are relative)

or are you trying to find 121 (11+22+88) which, as a non-array formula, is
=SUMPRODUCT(SUM(A$1:A$3)*A$1:A$3)



" wrote:

Thanks for the reply.

My example was poorly chosen since it does look as though I'm trying to
calculate the sum of squares.

I'm really trying to check that a set of eigenvectors are orthonormal.
I'm aiming to calculate

=SUMPRODUCT(X(i),X(j)) (via =SUM(X(i)*X(j)) )

where i,j = 1, ..., 31, and X(i) is a 31x1 column vector of real
values. The calculations are to be placed in a 31x31 matrix which
should be the identity matrix.

I have the eigenvectors in adjacent columns, so to pick them out as I
create the matrix, I'm using X(1) plus a column offset relative to the
first eigenvector.

Hope this helps to explain the situation. I'm certainly not saying it
is the most efficient approach.

Thanks again,

Clive