compare parts of strings

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ludvikjahn on 3 Mar 2015
Edited: Stephen23 on 4 Mar 2015
good morning, I want to know if there is a way to compare parts of strings in matlab.
For example: I want to find a string with 'dog':
compared to
should return:
In the same way, if I want to compare:
A=['red','green','yellow'] with
B=['greener', 'baseball', 'reddish'],
that should return either [1,1,0] or [1,0,1].
Just want to know if it is possible, because it seems quite impossible for my MATLAB skills.

Accepted Answer

Stephen23 on 3 Mar 2015
Edited: Stephen23 on 4 Mar 2015
In MATLAB the square brackets are not a list operator (as a lot of beginners think), but actually a concatenation operator , so your code:
simply concatenates all of those strings to give
which is probably not what you wanted. And
does nothing at all, because there is nothing to concatenate.
Instead you need to use a cell array to store the strings, like this:
>> A = {'dog','cat','ball','hot-dog','god','dogged'};
and 'dog' can simply be defined as a simple string like this
>> B = 'dog';
Then you can find the start indices of any match using strfind:
>> strfind(A,B)
ans =
[1] [] [] [5] [] [1]
which tell us the indices of where string B is found in each of the string in A. If you only need to know if the string exists in A then you can use cellfun on its output:
>> ~cellfun('isempty',strfind(A,B))
ans =
1 0 0 1 0 1
Likewise we can compare a cell array to see if there are any strings contained in the the strings of another cell array, although this is a little more code:
>> A = {'greener', 'baseball', 'reddish', 'mellow-yellow', 'greenspan'};
>> B = {'red', 'green', 'yellow'};
>> C = cellfun(@(s)strfind(A,s),B,'UniformOutput',false);
>> any(~cellfun('isempty',vertcat(C{:})),1)
ans =
1 0 1 1 1
You might also be interested in the matrix, which shows which substrings match between the two cell arrays (the rows=B, the columns=A):
>> ~cellfun('isempty',vertcat(C{:}))
ans =
0 0 1 0 0
1 0 0 0 1
0 0 0 1 0
Note that in all of these examples the code checks if the string/s in B exist in A.
  1 Comment
ludvikjahn on 3 Mar 2015
wow! that's very easy!

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