Find match for a pair of rows in cell arrays

Question

Stefano Alois 2016-9-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/305047-find-match-for-a-pair-of-rows-in-cell-arrays

评论： dpb 2016-9-29

采纳的回答： dpb

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I have 2 cell arrays of equal length, e.g.

>> alfa = {'a'; 'b'; 'c'; 'b'; 'a'; 'c'}

alfa =

    'a'
    'b'
    'c'
    'b'
    'a'
    'c'

>> beta = {'b'; 'd'; 'a'; 'd'; 'a'; 'a'}

beta =

    'b'
    'd'
    'a'
    'd'
    'a'
    'a'

and I want to find where the pairs are repeated, which pair is it and the index where the repeated pairs are located.

So, in this case the index 2 and 4 correspond to the repeated pair 'b' and 'd', and the index 3 and 6 correspond to the repeated pair 'c' and 'a'. It is important that I know which pair is it and all the indexes where this pair is repeated.

Thank you.

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Adam 2016-9-29

What is the significance of having two cell arrays? I don't see what the relevance of the 2nd one is other than just as another example. Is it supposed to be used in some way?

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Answer 1

dpb 2016-9-29

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https://ww2.mathworks.cn/matlabcentral/answers/305047-find-match-for-a-pair-of-rows-in-cell-arrays#answer_236650

编辑：dpb 2016-9-29

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Adam's on the right track, just didn't quite recognize the problem description--

>> ab=[char(alfa) char(beta)];  % mush the two arrays together
>> [u,ia,ib]=unique(ab,'rows'); % get the combinations that are extant
>> u(histc(ib,unique(ib))>1,:)  % find the ones with more than one occurrence
ans =
bd
ca
>>

The alternate returns from histc and unique will provide the positions.

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Answer 2

Adam 2016-9-29

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https://ww2.mathworks.cn/matlabcentral/answers/305047-find-match-for-a-pair-of-rows-in-cell-arrays#answer_236646

编辑：Adam 2016-9-29

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[C, ia, ic] = unique( alfa );

should give you this information. The C vector gives the characters and the ic vector tells you where they occur so repeated indices show the locations of the same letter.

[C, ia, ic] = unique( alfa )

C =

    'a'
    'b'
    'c'

ia =

     1
     2
     3

ic =

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Adam 2016-9-29

So what do you have? 2 arrays or 1 array of 6x2 size?

dpb 2016-9-29

He stated he had two cell arrays only you must consider them together by row--see my response. Simplest way is as done there to convert to a 1D character vector as the 'rows' option doesn't work for cellstr arrays, unfortunately. (Why not is anybody's guess... :( )

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