location of element in matrix

Question

jano satti 2017-4-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/337232-location-of-element-in-matrix

编辑： Andrei Bobrov 2017-4-25

采纳的回答： Andrei Bobrov

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I have a matrix mat and I want to find location of x in mat matrix.location should be in order of x.

mat =[

0000    1.0000    1.0000    1.0000    1.0000    1.0000
0099    1.0000    1.0000    0.0120    1.0000    0.0115
0093    1.0000    1.0000    0.0120    1.0000    0.0070
0000    1.0000    1.0000    1.0000    1.0000    1.0000
0098    1.0000    1.0000    0.0089    1.0000    0.0093
0000    1.0000    1.0000    1.0000    1.0000    1.0000];

x =[

    0.0089
    0.0099
    0.0070];
A =mat
  C=x
numbersInA = unique(C)
numbersInC = unique(C)
for k = 1 : length(numbersInA)
  [rowA colA] = find(A==numbersInC(k))
  w(k,:)= [rowA , colA]
end
ans is [ 3   6]
     [5     4]
     [2     1]
but I need this solution::
[5 4]
[2 1]
[3 6]
Thanks in advance.

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Stephen23 2017-4-25

编辑：Stephen23 2017-4-25

Do NOT use ismember ! See my answer for the reason why.

https://www.mathworks.com/matlabcentral/answers/337143-find-same-pair-values-from-two-variables#comment_448588

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Answer 1

Andrei Bobrov 2017-4-25

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/337232-location-of-element-in-matrix#answer_264450

编辑：Andrei Bobrov 2017-4-25

在 MATLAB Online 中打开

[l0,ii] = ismembertol(mat(:),x);
[i0,j0] = ind2sub(size(mat),find(l0));
[~,i1] = sort(ii(l0));
out = [i0,j0];
out = out(i1,:);

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Answer 2

Stephen23 2017-4-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/337232-location-of-element-in-matrix#answer_264451

Do NOT use ismember

Those are floating point values. It would be an extremely bad idea to use ismember on floating point values, because ismember tests for equivalence of the values. Really bad idea:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

https://www.mathworks.com/matlabcentral/answers/316183-floating-point-numeric-problem

https://www.mathworks.com/matlabcentral/answers/272092-basic-indexing-question-find-ismember

https://www.mathworks.com/matlabcentral/answers/328297-i-am-facing-a-problem-with-ismember-subfunciton-in-matlab

https://www.mathworks.com/matlabcentral/answers/281050-ismember-function-and-find-function-in-the-matlab-is-not-responding-for-some-values-please-check-th

Those values should be compared using a tolerance, or with ismembertol.