Excel turns off array formula mode when the result is a single value

Question

I have the following Worksheet array formula

{=MMULT(INDEX(Range1,1,{2,3,4}), Range2)}

where Range1 is a 1x4 matrix, and Range2 is a 3x1 matrix. I'd like the sum product of the horizontal vector and the vertical vector.

If my target range is a single cell, Excel strips away the array mode, and returned a #VALUE error because INDEX returns a 1x1 in the regular mode.

If my target range is a multi-cell range, it correctly calculates the sum and repeats for the entire range.

Is there any way to fix this? and get rid of the wrong optimization?

Answer 1

I'd like the sum product of the horizontal vector and the vertical vector.

In stead of your formula, you can use the following:

=MMULT(OFFSET(Range1,0,1,1,3), Range2)

It does not require to be entered as an array formula, although it is accepted if you do so.