# mmult with a 75 row matrix

Posted by Jaime Gomez on January 24, 2001 11:09 AM

Is there any limit at using excel for multiplying matrices? When I multiply a 75x50 matrix by a 50x75 matrix I get an "error". This error does not appear with a 73x50 matrix. Is there any way to solve this problem?

Thanks

Posted by Mark W. on January 24, 2001 12:01 PM

Jaime, you'll get a #VALUE! error if "...any cells are
empty or contain text, or if the number of columns in
array1 is different from the number of rows in array2."

Are either of the first two conditions true?

Posted by Jaime Gomez on January 25, 2001 1:29 AM

Thank you very much for your comment. I have checked the format of the data and I have also seen if I have any empty cell.

In relation to your second comment I do not think so, because I have transposed the first matrix in order to multiply it by the second.

=MMULT(B81:AY155;TRANSPOSE(B81:AY155))

In order to find where the problem is I have forgoten my data and created a new matrix. The result seems to be the same. When the number of rows is higher than 73 I get the same error.

I have installed Office 2000 and the problem keeps being the same. I am runnig Excel in a Pentium III with 128 MB.

Posted by Tim Francis-Wright on January 25, 2001 8:45 AM

I think that Excel is running into a problem
of having too many results in one array constant
(I had the same threshold that you did).

But, have no fear--you can still do the matrix
multiplication, just row-by-row:

=MMULT(B81:AY81;TRANSPOSE(\$B\$81:\$AY\$155))
will give the first row of the product matrix.
You can then copy the formula down as you need it.

Obviously, this is only a workaround and isn't
as nifty as ha1ving all of the answers in one
place.

Good luck!