# Function Question

#### ststern45

##### Well-known Member
I wanted to ask what the "--" before --(ISNUMBER function does to the formula?

Thanks!!

### Excel Facts

Quick Sum
Select a range of cells. The total appears in bottom right of Excel screen. Right-click total to add Max, Min, Count, Average.
ISNUMBER(...) returns TRUE or FALSE.
--ISNUMBER(...) (-1*-1*ISNUMBER(...) coerses that to their equivalent 1 or 0.

So, for example SUMPRODUCT(--ISNUMBER(MATCH(A1:A10, \$Z\$1:\$Z\$100, 0))) returns the number of cells in A1:A10 that are also in Z1:Z100.

SUMPRODUCT can not add up {TRUE; FALSE; TRUE; ...}, but it can add up {1; 0; 1; ...}

So by adding the "--" it will change a True/False to a 1 or 0. Where the 1 = True and a 0 = False. More or less like an on/off switch when it calculates a range(s) of cells?

Yes.

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