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Find index of cells containing my string

Asked by New on 25 Feb 2011
Latest activity Answered by Matt B on 14 Nov 2013

Hi, I have a cell aray (40,000X1)in which every cell contains a string. I would like to find the indexes of the cells containing a specific string.

I used the following:

Index = strfind(Mycellarray, 'Bla');

I get the following error: ??? Error using ==> cell.strfind at 35 If any of the input arguments are cell arrays, the first must be a cell array of strings and the second must be a character array.

What is wrong, in the help file strfind accepts cell arrays and a pattern...?

Thank you

5 Comments

New on 25 Feb 2011

Hi
Thank you for your answers. I used C2 = [C{:}] as advised but then still trying to get the list of Indices I used:
Index = strfind(C2,'bla')
I get a cell array in which every cell is either empty [] or 1 but no list of indices.
K.

Felipe on 22 Feb 2013

I found out that if the cell has empty indexes it wont work. Example:

a =

    'hey'
    'oh'
       []

>> strfind(a,'hey')

??? Error using ==> cell.strfind at 35 If any of the input arguments are cell arrays, the first must be a cell array of strings and the second must be a character array.

>> a{3} = 'letsGo'

a =

    'hey'
    'oh'
    'letsGo'

>> strfind(a,'hey')

ans =

    [1]
    []
    []

It is not considered as a cell string if all the cells in the array have a string in them.

Jan Simon on 22 Feb 2013

@Felipe: Exactly. A cell is a cell string, if it contains strings only. And STRFIND works on strings and cell strings only.

New

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4 Answers

Answer by Jan Simon on 25 Feb 2011
Edited by Jan Simon on 22 Feb 2013
Accepted answer

Do you want to search for the string 'bla' inside each string of the cell array, or should the cell element be 'bla' exactly? The answering would be easier, if you explain this detail.

If 'bla' should be part of the string:

C = [C{:}];   % [EDITED] Most likely this is not useful
IndexC = strfind(C, 'bla');
Index = find(not(cellfun('isempty', IndexC)));

If the string should be excatly 'bla': See Jos' answer.

2 Comments

Walter Roberson on 26 Feb 2011

Possibly bla might occur multiple times and the indices of all of the positions is what is desired?

Pooya89 on 3 Nov 2012

A little correction to Jan's answer:

   IndexC = strfind(C, 'bla'); % not C2
   ...

No need to convert C into string from cell : C2 = [C{:}];

Jan Simon
Answer by Matt B on 14 Nov 2013

I realize this question is old now, but a simple way of doing this is to define an inline function:

cellfind = @(string)(@(cell_contents)(strcmp(string,cell_contents)));

You can then use this with cellfun to return a boolean value for each element of the cell. For example:

cell_array={1,eye(2),true,'foo',10};
string='foo'
logical_cells = cellfun(cellfind('foo'),cell_array)
logical_cells = 
                 [0,0,0,1,0]

0 Comments

Matt B
Answer by Jos (10584) on 25 Feb 2011

So, your original array was a cell array of cells with a single string. Use STRCMP and FIND to get the indices of the cells with a cell containing the specified string

C = { {'a'}, {'b'}, {'c'}, {'a'}, {'a'} } % data
idx = find(strcmp([C{:}], 'a')) % single line engine

0 Comments

Jos (10584)
Answer by Jan Simon on 25 Feb 2011

You can check if your cell is a cell string:

iscellstr(Mycellarray);

This displays the indices and contents of the non-strings:

Index = find(~cellfun('isclass', Mycellarray, 'char'))
disp(Mycellarray(Index));

Another idea is, that some strings are multi-row CHAR matrices:

Index = find(cellfun('size', Mycellarray, 1) > 1)

0 Comments

Jan Simon

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