I have matrix A, how can I add a row in matrix A with others rows of matrix A ?

Question

Firzi Mukhri 2013-5-29

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https://ww2.mathworks.cn/matlabcentral/answers/77283-i-have-matrix-a-how-can-i-add-a-row-in-matrix-a-with-others-rows-of-matrix-a

For example:

a = ones (220,220);
b = a(:,1)+a(:,11)+a(:,21)+     a(:,31)+a(:,41)+a(:,51)+a(:,61)+a(:,71)+a(:,81)+a(:,91);

I would like to obtain sum of row as b. The problem is the matrix I'm working on is thousands, is there a more easy way to do this? a certain function maybe that only needs me to specify the column number. Thank you!

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Answer 1

Matt Kindig 2013-5-29

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https://ww2.mathworks.cn/matlabcentral/answers/77283-i-have-matrix-a-how-can-i-add-a-row-in-matrix-a-with-others-rows-of-matrix-a#answer_86932

在 MATLAB Online 中打开

b = sum(a(:,1:10:91),2)

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Firzi Mukhri 2013-5-29

it works! but what is the number 2 represent?

Matt Kindig 2013-5-29

2 is the dimension over which the summing is performed. Dimensions are ordered in the same order that they are returned from the size() function, i.e. dimension=1 is sum down the rows, dimension=2 is sum down the columns, dimension=3 is sum across dimension 3 ("planes"), etc.

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