Find substring in cell array of numbers and strings - matlab

Question

I have a cell array consisting of numbers, strings, and empty arrays. I want to find the position (linear or indexed) of all cells containing a string in which a certain substring of interest appears.
mixedCellArray = {
'adpo' 2134 []
0 [] 'daesad'
'xxxxx' 'dp' 'dpdpd'
}
If the substring of interest is 'dp', then I should get the indices for three cells.
The only solutions I can find work when the cell array contains only strings:
http://www.mathworks.com/matlabcentral/answers/2015-find-index-of-cells-containing-my-string
http://www.mathworks.com/matlabcentral/newsreader/view_thread/255090
One work-around is to find all cells not containing strings, and fill them with '', as hinted by this posting. Unfortunately, my approach requires a variation of that solution, probably something like cellfun('ischar',mixedCellArray). This causes the error:
Error using cellfun
Unknown option.
Thanks for any suggestions on how to figure out the error.
I've posted this to usenet
EDUCATIONAL AFTERNOTE: For those who don't have Matlab at home, and end up bouncing back and forth between Matlab and Octave. I asked above why cellfun doesn't accept 'ischar' as its first argument. The answer turns out to be that the argument must be a function handle in Matlab, so you really need to pass #ischar. There are some functions whose names can be passed as strings, for backward compatibility, but ischar is not one of them.

Answer 1

How about this one-liner:
>> mixedCellArray = {'adpo' 2134 []; 0 [] 'daesad'; 'xxxxx' 'dp' 'dpdpd'};
>> index = cellfun(#(c) ischar(c) && ~isempty(strfind(c, 'dp')), mixedCellArray)
index =
3×3 logical array
1 0 0
0 0 0
0 1 1
You could get by without the ischar(c) && ..., but you will likely want to keep it there since strfind will implicitly convert any numeric values/arrays into their equivalent ASCII characters to do the comparison. That means you could get false positives, as in this example:
>> C = {65, 'A'; 'BAD' [66 65 68]} % Note there's a vector in there
C =
2×2 cell array
[ 65] 'A'
'BAD' [1×3 double]
>> index = cellfun(#(c) ~isempty(strfind(c, 'A')), C) % Removed ischar(c) &&
index =
2×2 logical array
1 1 % They all match!
1 1

Answer 2

Just use a loop, testing with ischar and contains (added in R2016b). The various *funs are basically loops and, in general, do not offer any performance advantage over the explicit loop.
mixedCellArray = {'adpo' 2134 []; 0 [] 'daesad'; 'xxxxx' 'dp' 'dpdpd'};
querystr = 'dp';
test = false(size(mixedCellArray));
for ii = 1:numel(mixedCellArray)
if ischar(mixedCellArray{ii})
test(ii) = contains(mixedCellArray{ii}, querystr);
end
end
Which returns:
test =
3×3 logical array
1 0 0
0 0 0
0 1 1
Edit:
If you don't have a MATLAB version with contains you can substitute a regex:
test(ii) = ~isempty(regexp(mixedCellArray{ii}, querystr, 'once'));

Answer 3

z=cellfun(#(x)strfind(x,'dp'),mixedCellArray,'un',0);
idx=cellfun(#(x)x>0,z,'un',0);
find(~cellfun(#isempty,idx))

Answer 4

Here is a solution from the usenet link in my original post:
>> mixedCellArray = {
'adpo' 2134 []
0 [] 'daesad'
'xxxxx' 'dp' 'dpdpd'
}
mixedCellArray =
'adpo' [2134] []
[ 0] [] 'daesad'
'xxxxx' 'dp' 'dpdpd'
>> ~cellfun( #isempty , ...
cellfun( #(x)strfind(x,'dp') , ...
mixedCellArray , ...
'uniform',0) ...
)
ans =
1 0 0
0 0 0
0 1 1
The inner cellfun is able to apply strfind to even numerical cells because, I presume, Matlab treats numerical arrays and strings the same way. A string is just an array of numbers representing the character codes. The outer cellfun identifies all cells for which the inner cellfun found a match, and the prefix tilde turns that into all cells for which there was NO match.
Thanks to dpb.