MATLAB Answers

Find index of cells containing my string

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New
New 25 Feb 2011
댓글: per isakson 22 May 2020
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

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Jan
Jan 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.
Yusuf Arslan
Yusuf Arslan 26 Sep 2017
Hello, I have got a similar Problem.
- find(strcmp(rawdata,'ggiBoundaries1(1,1)'))
I want to find in rawdata the first entry of ggiBoundaries1. But it doesn't work. The error message is =
"0×1 empty double column vector".
When I enter "ggiBoundaries1(1,1)" the output is a char. Maybe that's the problem or not?
Jan
Jan 26 Sep 2017
This is not an error message. It simply tells you, that the string is not found.
Are you really looking for the string 'ggiBoundaries1(1,1)' ? Or do you mean:
find(strcmp(rawdata, ggiBoundaries1(1,1)))
to search for occurrences of the first character of the variable ggiBoundaries1?
Please do not append a new question to an existing thread. Better open a new one. Thanks.

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채택된 답변

Jan
Jan 25 Feb 2011
편집: MathWorks Support Team 8 Nov 2018
Do you want to search for 'bla' within the text in each element of the cell array, or for elements that are 'bla' exactly? If you explain this detail, then your question would be easier to answer.
If you are searching for text that has 'bla' as part of the text, then starting in R2016b you can use the “contains” function, as Alexander Cranney pointed out.
Index = find(contains(C,'bla'));
In previous versions of MATLAB, you can use the “strfind” function. However, “strfind” returns a cell array of indices. For any input cell whose text does not contain 'bla', “strfind” returns an empty cell. Use “isempty” and “cellfun” with the “find” function to find the empty cells.
IndexC = strfind(C,'bla');
Index = find(not(cellfun('isempty',IndexC)))
If you are searching for text that is exactly 'bla', then see Jos’ answer.

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Jan
Jan 12 Jun 2018
@Duc Minh Nguyen: As said in the answer, it is the purpose of the code to find any occurrences of 'bla', not just the string 'bla'.
ANA ROSHAN
ANA ROSHAN 10 Feb 2020
it was very useful. thanks!
Nnamdi Njoku
Nnamdi Njoku 22 May 2020
Just what i needed, thanks

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추가 답변(7개)

Jay
Jay 28 May 2016
편집: Jay 28 May 2016
This worked for me:
idx = find(ismember(C, 'bla'))

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Einat
Einat 5 Jun 2019
Yes! Worked just like I needed it to.
ANKUR WADHWA
ANKUR WADHWA 17 Jan 2020
Doesn't work on this one
C = { {'a'}, {'b'}, {'c'}, {'a'}, {'a'};{'b'}, {'a'}, {'c'}, {'a'}, {'c'} }
idx = find(strcmp([C{:}], 'a'))
Returns
idx = 1 4 7 8 9
Any suggestion on how to solve it.
per isakson
per isakson 22 May 2020
It works as documented.
Matlab uses column-major order. (I fail to find a page to link to in the documentation.)
Try
%%
C = { {'a'}, {'b'}, {'c'}, {'a'}, {'a'}
{'b'}, {'a'}, {'c'}, {'a'}, {'c'} };
%%
cac = [C{:}]
idx = find(strcmp( cac, 'a' ))
%%
C1 = permute( C, [2,1] ); % switch rows and columns
idx = find(strcmp( [C1{:}], 'a' ))
it outputs
cac =
1×10 cell array
Columns 1 through 8
{'a'} {'b'} {'b'} {'a'} {'c'} {'c'} {'a'} {'a'}
Columns 9 through 10
{'a'} {'c'}
idx =
1 4 7 8 9
idx =
1 4 5 7 9

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Matt B
Matt B 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]

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Sepp
Sepp 27 Feb 2016
Great answer. Works very well.
josh gore
josh gore 26 Jan 2017
The inline function was a life saver!
Jan
Jan 6 Jun 2019
@Matt B: strcmp accepts a cell array directly, so you can avoid the complicated cellfun approach with the expensive anonymous function:
cell_array = {1,eye(2),true,'foo',10}
strcmp(cell_array, 'foo')
>> [0,0,0,1,0]

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Jos (10584)
Jos (10584) 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

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AATIQ OUSSAMA
AATIQ OUSSAMA 16 Apr 2017
Thanks Jos , It works fine !

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Omer Moussaffi
Omer Moussaffi 26 Feb 2017
Faster options: count startsWith endsWith
E,g, Index = count(Mycellarray, 'Bla');

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Walter Roberson
Walter Roberson 26 Feb 2017
Yes, this method should work well starting from R2016b.

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Jan
Jan 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)

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Peter Farkas
Peter Farkas 9 May 2016
You can also explicitelly define the index matrix:
[rw, ~] = size(cellArray);
ind = [1:1:rw];
idx = strcmp(cellArray, stringToSearchFor);
yourResult = ind(idx);
It is kind of verbose, if you review the code in 2 years time, you will still know what is going on.

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Mukesh Jadhav
Mukesh Jadhav 9 Oct 2016
편집: per isakson 10 Jan 2017
Haven't tested but this should work fine.
word_to_find=strfind(strarray,'stringtofind');
starray.index(word_to_find);

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