SUMPRODUCT Question

V

Victor Chapman

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
 
B

Biff

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 here:

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

Biff
 
J

JulieD

Hi Victor

Probably the best reference for information on the sumproduct function that
i know about is at

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

But basically the sumproduct function works by evaluation true statements to
1 and false statements to 0 ...

For a quick overview of your sumproduct funtion look at it this way:
=SUMPRODUCT((WEEK=$A43) * Duration)
=SUMPRODUCT((D3:H41 =$A43)*B3:B41)
(for this example i'm make the ranges smaller .... e.g.)
=SUMPRODUCT((D1:F3 =$G1)*B1:B3)
(and use the following data)
.......A........B.........C.........D........E.........F.............G
1.............10...................Bill......Fred....Steve.......Anne
2.............15...................Anne...Bill.......Fred........Bill
3.............20...................Fred....Anne....Steve......Steve

In G2 the SUMPRODUCT formula would work like this
=SUMPRODUCT((D1:F3 =$G1)*B1:B3)
=SUMPRODUCT((Bill, Fred, Steve, Anne, Bill, Fred, Fred, Anne,
Steve=Anne)*(10,10,10,15,15,15,20,20,20))
=SUMPRODUCT((False, False, False, True, False, False, False, True,
False)*(10,10,10,15,15,15,20,20,20))
=SUMPROUDCT((0,0,0,1,0,0,0,1,0)*(10,10,10,15,15,15,20,20,20))
=SUMPRODUCT(0*10+0*10+0*10+1*15+0*15+0*15+0*20+1*20+0*20)
=SUMPRODUCT(0+0+0+15+0+0+0+20+0)
=35

Hope this helps.

--
Cheers
JulieD
Excel MVP

julied_ng at hctsReMoVeThIs dot net dot au
 
V

Victor Chapman

JulieD said:
Hi Victor

Probably the best reference for information on the sumproduct function that
i know about is at

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

But basically the sumproduct function works by evaluation true statements to
1 and false statements to 0 ...

For a quick overview of your sumproduct funtion look at it this way:
=SUMPRODUCT((WEEK=$A43) * Duration)
=SUMPRODUCT((D3:H41 =$A43)*B3:B41)
(for this example i'm make the ranges smaller .... e.g.)
=SUMPRODUCT((D1:F3 =$G1)*B1:B3)
(and use the following data)
......A........B.........C.........D........E.........F.............G
1.............10...................Bill......Fred....Steve.......Anne
2.............15...................Anne...Bill.......Fred........Bill
3.............20...................Fred....Anne....Steve......Steve

In G2 the SUMPRODUCT formula would work like this
=SUMPRODUCT((D1:F3 =$G1)*B1:B3)
=SUMPRODUCT((Bill, Fred, Steve, Anne, Bill, Fred, Fred, Anne,
Steve=Anne)*(10,10,10,15,15,15,20,20,20))
=SUMPRODUCT((False, False, False, True, False, False, False, True,
False)*(10,10,10,15,15,15,20,20,20))
=SUMPROUDCT((0,0,0,1,0,0,0,1,0)*(10,10,10,15,15,15,20,20,20))
=SUMPRODUCT(0*10+0*10+0*10+1*15+0*15+0*15+0*20+1*20+0*20)
=SUMPRODUCT(0+0+0+15+0+0+0+20+0)
=35

Hope this helps.
Click to expand...
Thank you for your quick response. I agree, and understand that this is
what the function is doing. What I don't understand is why this works
when it it would appear to be contrary to the information provided in
the Excel Help system. The following is copied from the Help system:

The array arguments must have the same dimensions. If they do not,
SUMPRODUCT returns the #VALUE! error value.

In the example I have provided, Duration is a single column array. WEEK
on the other hand is a multiple column matrix. They have different
dimensions!

To work from your example:

=SUMPRODUCT((D1:F3 =$G1)*B1:B3)

is NOT the same as

=SUMPRODUCT((Bill, Fred, Steve, Anne, Bill, Fred, Fred, Anne,
Steve=Anne)*(10,10,10,15,15,15,20,20,20))

It makes the assumption that for every instance of a row value in WEEK,
the corresponding row value in Duration will be generated. I can't find
anywhere in the documentation that I can make that assumption. I have
also checked http://www.xldynamic.com/source/xld.SUMPRODUCT.html and
cannot find an example similar to the one I have provide.
 
A

Aladin Akyurek

Victor said:
Thank you for your quick response. I agree, and understand that this is
what the function is doing. What I don't understand is why this works
when it it would appear to be contrary to the information provided in
the Excel Help system. The following is copied from the Help system:

The array arguments must have the same dimensions. If they do not,
SUMPRODUCT returns the #VALUE! error value.

In the example I have provided, Duration is a single column array. WEEK
on the other hand is a multiple column matrix. They have different
dimensions!

To work from your example:

=SUMPRODUCT((D1:F3 =$G1)*B1:B3)

is NOT the same as

=SUMPRODUCT((Bill, Fred, Steve, Anne, Bill, Fred, Fred, Anne,
Steve=Anne)*(10,10,10,15,15,15,20,20,20))

It makes the assumption that for every instance of a row value in WEEK,
the corresponding row value in Duration will be generated. I can't find
anywhere in the documentation that I can make that assumption. I have
also checked http://www.xldynamic.com/source/xld.SUMPRODUCT.html and
cannot find an example similar to the one I have provide.
Click to expand...

You are multiplying, as it were, a vector with a matrix which are
equally sized in one relevant dimension.
 
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