excel SUMPRODUCT function Using SUMPRODUCT with boolean arrays
Example
Consider the following ranges A1:A3 and B1:B3 as below
=SUMPRODUCT(--(A1:A3="c"),B1:B3)
This will first manipulate (A1:A3="c") into the following array
A1="c" = FALSE
A2="c" = FALSE
A3="c" = TRUE
Then apply the -- operator which converts TRUE and FALSE into 1 and 0, respectively. So the array becomes
--FALSE = 0
--FALSE = 0
--TRUE = 1
Then the SUMPRODUCT formula completes as in the simple numeric case. Returning 6 in this example
0*4 = 0
0*5 = 0
1*6 = 6
Note: this is the equivalent of a SUMIF function
