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Vector Dot-Product in Microsoft Excel

Dot-product, or rather vector dot-product, does not have a familiar phrase to use in Microsoft Excel. For instance, if you want to perform the following operation,

=(A1*B1)+(A2*B2)+(A3*B3)+...+(AK*BK)

which exactly resembles that of a vector dot-product; that is, A*B where A = [A1 A2 ... AK] and B = [B1 B2 ... AK]T.

(Quick way to obtain the dot-product in Excel...)

Here is the quick way to do that in Microsoft Excel.

For the similar expression above, simply use the built-in function, SUMPRODUCT(). For example,

=SUMPRODUCT(A1:AK,B1:BK)

And the resulting vector dot-product is easily calculated with Microsoft Excel.

Why can't they put this in the help file?

Why, oh why, can't Microsoft include something in the Help file that would let me find this? A cross reference to dot-product, or vector, or array? Arrgh!