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

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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

Answers (2)

John D'Errico
John D'Errico on 1 Jun 2017
What is it called? A sum.
help sum
Or if you insist on doing it as a multiply, then
help ones
help mtimes

Christoph F.
Christoph F. on 1 Jun 2017
That is just a regular matrix multiplication, with the second "matrix" having only one column.
  1 Comment
Rehan Rehan
Rehan Rehan on 1 Jun 2017
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.

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