Hi!

(WEEK=$A43) will return an array of boolean TRUE or FALSE. Something like
this:

D3 = A43 = TRUE
D4 = A43 = FALSE
D5 = A43 = TRUE
D6 = A43 = FALSE

Then those boolean values are multiplied by the corresponding duration
values from the other array, B3:B41. That would look like this:

TRUE * B3 = B3
FALSE * B4 = 0
TRUE * B5 = B5
FALSE * B6 = 0

Then the values are summed together and you get your result.

There's a very detailed explanation of Sumproduct he

http://www.xldynamic.com/source/xld.SUMPRODUCT.html

Biff

"Victor Chapman" wrote in message
. ..
This maybe a strange question, but I have a SUMPRODUCT function that works
in Excel, however, I don't understand why it does.

Here is what I have:

An array of task times (Duration) B3:B41

A matrix of names of people assigned to the various tasks throughout the
week (WEEK)D3:H41 (The names appear one or more times)

The array of individual names appears in A43:A61

Now I want to know the total time each individual spends carrying out one
or more of the tasks. This is done with:

SUMPRODUCT((WEEK=$A43) * Duration)

This function appears beside each name with the row number incremented
accordingly. IT WORKS!

Here is my problem, I can't find anywhere in the documentation for this
function (or another example) where a row number in a matrix will look up
the corresponding row number in an array. So I don't understand why it
provides the desired result.

I would appreciate more examples of this use of SUMPRODUCT and technical
explanation of why it works.

TIA



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_______________________________
Regards,
Vic Chapman