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Inquiry regarding matrix multiplication

Forum|Forum|1 year ago
May 9, 2024
2 replies
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Dear Mathcad community,

I am writing my first post on this forum in the hope that someone can assist me with a question. Firstly, I would like to say that I am using Mathcad Prime 9.0.0.0. and I am attempting to multiply two matrices and I am struggling to achieve my objective. I want to multiply matrix A (with i rows and j columns) by matrix B (with j rows and 1 column), in order to obtain matrix C as shown in the image (with i rows and j columns). Subsequently, I aim to determine the maximum value of each row in C later.

Thank you very much in advance for your assistance.

Sincerely, Germán.

Captura de pantalla 2024-05-09 091212.png

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Best answer by Werner_E

Oh my goodness!
That's another one of those "Why didn't I think of that in the first place?" moments!

The easiest way to create the matrix you are looking for sure is

without having to write and use any 'create'-function.

You may also use it with symbolic evaluation if you need to do so

The get the max values of each row you may still use the function I posted before.

ttokoro

21-Topaz I

t.t.

G

Germán

Author

8-Gravel

Thank you ttokoro for your reply. I don't know the reason why your solution doesn't work well in my Mathcad, probably I implemented it in a wrong way:

Captura de pantalla 2024-05-14 081419.png

But it gave me an idea to solve it, as follows:

Captura de pantalla 2024-05-14 081518.png

Thank you very much.

W

Werner_E

25-Diamond I

@ttokoro

Wouldn't it be much easier to simply use

😉

@Germán

@Germán wrote:

I am attempting to multiply two matrices

NO!! You are NOT looking for matrix multiplication. Prime knows how to multiply two matrices (given the dimensions are correct) but what you are looking for is NOT called matrix multiplication.

So its best to write a small user-function which takes the two matrices as its input and return a matrix according to your specifications.

The same applies for the max values in each row.

Here are my suggestions (note that there is no error checking implemented to throw an error if the matrix dimensions are not correct (second matrix is only allowed one column and must have same number of rows as are columns in the first matrix):