How to find the number of different strings in a cell array?

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Faranak 2017-10-3

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编辑： Cedric 2017-10-3

Hi, I have a cell with different strings. I don't know what are those strings and how many times they are repeated. I want to find the names of strings and find how many they are repeated. For example: c={'a' 'a' 'a' 'a' 'b' 'b' 'b' 'c' 'c' 'd' 'e'}; I want the answer to say that strings are a,b,c,d,e and the numbers they are repeating are 4,3,2,1,1.

I tried strfind command but it is good for a time that you know what are the strings (which I don't know what are the strings!). I tried strcmp command to find how many each are repeated. But still I have problem with finding the strings! Can anyone help me?

Thanks

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Answer 1

Cedric 2017-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/359542-how-to-find-the-number-of-different-strings-in-a-cell-array#answer_284177

编辑：Cedric 2017-10-3

在 MATLAB Online 中打开

Use

uc = unique(c) ;

to get a cell array of unique strings, and its length is their count.

If you need a stat of repetition, use the 2nd or 3rd output of UNIQUE and accumulate ones using it as IDs in acall to ACCUMARRAY.

I can't test right now, but something like

 [uc, ~, idc] = unique( c ) ;
 counts = accumarray( idc, ones(size(idc)) ) ;

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Faranak 2017-10-3

Thank you so much. It was perfect.

Cedric 2017-10-3

编辑：Cedric 2017-10-3

My pleasure! Look at Walter's answer and ImageAnalyst example; FINDGROUPS and HISTCOUNTS may be simpler to (re-)understand if you look back at your code in a few years.

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Answer 2

Walter Roberson 2017-10-3

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For R2015b or later, use findgroups()

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Image Analyst 2017-10-3

在 MATLAB Online 中打开

E.g.

c={'a' 'a' 'a' 'a' 'b' 'b' 'b' 'c' 'c' 'd' 'e' 'a' 'a' };
[d, id] = findgroups(c)
counts = histcounts(d)
d =
     1     1     1     1     2     2     2     3     3     4     5     1     1
id =
  1×5 cell array
    {'a'}    {'b'}    {'c'}    {'d'}    {'e'}
counts =
     6     3     2     1     1