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

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Rehan Rehan 2017-6-1

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评论： Rehan Rehan 2017-6-1

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

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Answer 1

John D'Errico 2017-6-1

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在 MATLAB Online 中打开

What is it called? A sum.

help sum

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

help ones
help mtimes

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Answer 2

Christoph F. 2017-6-1

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

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Rehan Rehan 2017-6-1

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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