Finding element with max value in each row of a matrix

Question

Konstantinos 2014-12-4

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评论： Konstantinos 2014-12-4

How can I find the 4 elements with the largest values in each row of a matrix ? Moreover, I would like to know the exact position of them in each row.

i.e. A(2X8) = [ 1 2 3 4 8 5 2 9 ; 5 6 4 7 9 1 1 2; ]

For the above matrix the answer would be:

1st row max values elements: 4, 8, 5, 9

1st row position of these elements: 4, 5, 6, 8

2nd row max values elements: 5, 6, 7, 9

2nd row position of these elements: 1, 2, 4, 5

Any help could be useful.

Thanks in advance!

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Answer 1

Azzi Abdelmalek 2014-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/165389-finding-element-with-max-value-in-each-row-of-a-matrix#answer_161242

编辑：Azzi Abdelmalek 2014-12-4

在 MATLAB Online 中打开

a=[ 1 2 3 4 8 5 2 9 ; 5 6 4 7 9 1 1 2; ]
[ii,jj]=sort(a,2,'descend')
v=ii(:,1:4)
idx=jj(:,1:4)

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Konstantinos 2014-12-4

Thanks a lot!

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Answer 2

Guillaume 2014-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/165389-finding-element-with-max-value-in-each-row-of-a-matrix#answer_161241

编辑：Guillaume 2014-12-4

在 MATLAB Online 中打开

sort your matrix by column and in descending order. The first argument returned are the max, the second their indices:

A = [1 2 3 4 8 5 2 9 ; 5 6 4 7 9 1 1 2]
[maxvals, maxindices] = sort(A, 2, 'descend');
maxvals = maxvals(:, 1:4)
maxindices = maxindices(:, 1:4)

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Guillaume 2014-12-4

Yes, I forgot the colon initially. However, I corrected that mistake before you made the comment.

My answer is identical to Azzi's except mine got some explanation (and useful variable names).

Konstantinos 2014-12-4

You are correct! thanks for your help!

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