Please help with using accumarray to choose the max value of the array

Question

Hashini Wanniarachchi 2020-3-18

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评论： Hashini Wanniarachchi 2020-3-18

I have a matrix, for an example with 11 x 3.

CH BA OL

10.0000 10.0000 0.6000

10.0000 11.0000 0.4000

11.0000 9.0000 0.6000

11.0000 10.0000 0.2000

11.0000 11.0000 0.2000

25.0000 44.0000 0.1000

25.0000 9.0000 0.7000

25.0000 45.0000 0.2000

27.0000 44.0000 0.2000

27.0000 46.0000 0.3000

27.0000 9.0000 0.5000

I'm trying to take unique values for column CH, and each unique value in CH should sort the maximum value's BA. For example, final results should be like

CH BA OL

10 10 0.6

11 9 0.6

25 9 0.7

27 46 0.5

I was trying accumarray but I couldnt get the correct answer. Please help

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Ameer Hamza 2020-3-18

In that case, last row should be 27 9 0.5

Hashini Wanniarachchi 2020-3-18

I apologize for the confusion!

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Answer 1

Mohammad Sami 2020-3-18

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https://ww2.mathworks.cn/matlabcentral/answers/511460-please-help-with-using-accumarray-to-choose-the-max-value-of-the-array#answer_420667

在 MATLAB Online 中打开

% matrix = 11 x 3
ch = matrix(:,1);
[u,~,ic] = unique(ch);
maxba = accumarray(ic,matrix(:,2),[],@max);
out = [u maxba];
i = ismember(matrix(:,1:2),out,'rows');
out = matrix(i,:);

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Hashini Wanniarachchi 2020-3-18

Thank you so much for guidance. Well I wanted to sort through col 3. I sorted it out anyhow following this. Thanks again!

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Answer 2

Ameer Hamza 2020-3-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/511460-please-help-with-using-accumarray-to-choose-the-max-value-of-the-array#answer_420673

编辑：Ameer Hamza 2020-3-18

在 MATLAB Online 中打开

Try this

M = [10.0000   10.0000    0.6000
   10.0000   11.0000    0.4000
   11.0000    9.0000    0.6000
   11.0000   10.0000    0.2000
   11.0000   11.0000    0.2000
   25.0000   44.0000    0.1000
   25.0000    9.0000    0.7000
   25.0000   45.0000    0.2000
   27.0000   44.0000    0.2000
   27.0000   46.0000    0.3000
   27.0000    9.0000    0.5000];
[~,idx] = sort(M(:,3));
M = M(idx,:);
[~,idx] = sort(M(:,1));
M = M(idx,:);
result = splitapply(@(x) x(end,:), M, findgroups(M(:,1)));