Hi Bob,

I was writing my own reply while you posted your answer. As I say in my
post, I have still not fully understood when ={...} works. In the post
I reflect my current understanding of this.

Can you please explain why your formula works? I tested it in my own
test data set and verified that its philosophy works. One thing I have
come to conclude myself since I wrote the post is that SUMPRODUCT,
without array entering, will accept as arguments computed arrays if
they are the result of operations. If however, the computed array is
the result of a function, then it needs array entering.

Yet, I am still puzzled by some things:

- In a column with values in {"A", "B", "C"} the following formula does
not work:
=IF(J3={"A","B"}, 1, 0)

If I simply enter it, then it produces #VALUE!.
If I array-enter it, it only recognizes the "A", consistent with the
behavior when an array is used in a formula, in a place where a scalar
is expected.
However, it obviously works in the following, same philosophy as your
formula, i.e. without array-entering:
=SUMPRODUCT(K2:K15*(J2:J15={"A","B"}))

This I cannot explain. Can you enlighten please?

Regards,
Kostis Vezerides