Find set of values that are unique to the values in another column

Question

Elian Ricardo Gonzalez Beltran 2019-11-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/492521-find-set-of-values-that-are-unique-to-the-values-in-another-column

回答： Stephen23 2019-11-22

采纳的回答： Erivelton Gualter

I have a matrix like the following.

2 3

2 6

2 8

4 5

5 9

5 39

5 6

I need to do operations on numbers in the second column based on the values in the first column. It should be for the unique vaue "2", mean of (3,6,8) etc. Any help is appreciated. Thanks

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Answer 1

Erivelton Gualter 2019-11-22

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% Mqtrix
A =[2 3;
    2 6
    2 8
    4 5
    5 9
    5 39
    5 6]
% Get unique values on first collumn
un = unique(A(:,1)); % un = [2 4 5]
% Output
A(A(:,1)==un(1),2)

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Answer 2

Andrei Bobrov 2019-11-22

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https://ww2.mathworks.cn/matlabcentral/answers/492521-find-set-of-values-that-are-unique-to-the-values-in-another-column#answer_402747

[G,d] = findgroups(A(:,1));
out = [d,splitapply(@mean,A(:,2),G)];

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Answer 3

Stephen23 2019-11-22

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https://ww2.mathworks.cn/matlabcentral/answers/492521-find-set-of-values-that-are-unique-to-the-values-in-another-column#answer_402755

>> M = [2,3;2,6;2,8;4,5;5,9;5,39;5,6]
M =
    2    3
    2    6
    2    8
    4    5
    5    9
    5   39
    5    6
>> [U,~,X] = unique(M(:,1));
>> V = accumarray(X,M(:,2),[],@mean);
>> [U,V]
ans =
    2.0000    5.6667
    4.0000    5.0000
    5.0000   18.0000