explanation of dashes

rs2k

Well-known Member
Joined
Aug 15, 2004
Messages
1,413
Could anyone point me in the right direction or explain what the two dashes mean in some formulas, (an example below has been copied from a random post)
=SUMPRODUCT(--($A$2:$A$10=G$2),--($B$2:$B$10=$F3),$C$2:$C$10)

Thanks
Colin.
 

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Aladin Akyurek

MrExcel MVP
Joined
Feb 14, 2002
Messages
85,210
rs2k said:
Could anyone point me in the right direction or explain what the two dashes mean in some formulas, (an example below has been copied from a random post)
=SUMPRODUCT(--($A$2:$A$10=G$2),--($B$2:$B$10=$F3),$C$2:$C$10)

Thanks
Colin.

That "random post" wasn't that random... :LOL:

See:

http://www.mrexcel.com/board2/viewtopic.php?t=73205

At the risk of repeating what is already known, the syntax of SumProduct is:

SUMPRODUCT(Array1,Array2,...)

SumProduct multiplies the arrays it is given. The result of that multiplication is also an array, which SumProduct sums. Multiplication and summing say it all: Those arrays must all be numeric, that is, consist of numbers.

If you use a CONDITIONAL like

$A$2:$A$10=G$2

instead of a numeric array, the result of the evaluation of the conditional will be an array/vector of truth values, something like:

{TRUE;FALSE;FALSE;FALSE;TRUE;FALSE;FALSE;FALSE;TRUE}

an object SumProduct cannot do multiplication with. Fortunately, as we know, Excel also have numeric equivalents for the truth values of TRUE and FALSE.

We also know something called COERCION, that is, changing from one data type to another. In case of the truth values, the following effects coercion from logical to numeric equivalents:

=--TRUE ===> 1
=TRUE+0 ===> 1
=TRUE*1 ===> 1
=TRUE^1
=N(TRUE)

If you substitute FALSE for TRUE above, youl'll get 0.

From above:

--($A$2:$A$10=G$2)

will give:

{1;0;0;0;1;0;0;0;1}

0's help to eliminate irrelevant numbers in other arrays/vectors.

Note that the so-called "array formulas" operate the same way.

Edit for typo's.
 
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rs2k

Well-known Member
Joined
Aug 15, 2004
Messages
1,413
Many thanks for the replies,
I will go and play with it for a bit now.

Cheer's
Colin.
 
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