Matrix Multiplication by a vector of Ones - How to write mathematically

Hi,

During my calculations I come at a point where I multiply say 9x9 matrix by a column vector containing ONEs of size 9x1. Definitely, it returns me a vector of 9x1 with all columns summed into single element.

What is such process called mathematically and how to write it in notation?

I will grateful for the help.

Best regards, Rehan

Answer 1

[John D'Errico]

What is it called? A sum.

help sum

Or if you insist on doing it as a multiply, then

help ones
help mtimes

Answer 2

[Christoph F.]

That is just a regular matrix multiplication, with the second "matrix" having only one column.

[Rehan Rehan]

Thanks for the reply.

Of course, that is how it is performed but my question was from matrix algebra point of view. In case there exists a "name" of such operation or any evidence where it is utilized.