MATLAB Answers

Find index of cells containing my string

5,040 views (last 30 days)
New
New on 25 Feb 2011
Commented: ANKUR WADHWA on 17 Jan 2020 at 10:24
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

  7 Comments

Show 4 older comments
Jan
Jan 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.
Yusuf Arslan
Yusuf Arslan on 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 on 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.

Sign in to comment.

Accepted Answer

Jan
Jan on 25 Feb 2011
Edited: MathWorks Support Team on 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.

  6 Comments

Show 3 older comments
xiangxue wang
xiangxue wang on 5 Nov 2017
Just to add my experience of running this. If the cell C contains some entry will NaN, it will gave the error like "First argument must be a string array, character vector, or cell array of character vectors" make sure your cell doesn't contain NaN
Duc Minh Nguyen
Duc Minh Nguyen on 12 Jun 2018
This answer will cause problem if there are other strings containing 'bla' in the array. For exact searching, use strcmp instead:
idx = find(strcmp(C, 'bla'))
Jan
Jan on 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'.

Sign in to comment.

More Answers (7)

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

  6 Comments

Show 3 older comments
juliette Grimaldi
juliette Grimaldi on 20 Dec 2017
Great, thanks! Old stuff still makes it !
Einat
Einat on 5 Jun 2019
Yes! Worked just like I needed it to.
ANKUR WADHWA
ANKUR WADHWA 16 minutes ago
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.

Sign in to comment.


Matt B
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]

  3 Comments

Sepp
Sepp on 27 Feb 2016
Great answer. Works very well.
josh gore
josh gore on 26 Jan 2017
The inline function was a life saver!
Jan
Jan on 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]

Sign in to comment.


Jos (10584)
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

  1 Comment

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

Sign in to comment.


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

  1 Comment

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

Sign in to comment.


Jan
Jan 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

Sign in to comment.


Peter Farkas
Peter Farkas on 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.

  0 Comments

Sign in to comment.


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

  0 Comments

Sign in to comment.

Sign in to answer this question.