Testing for the presence of a substring in a cell array of strings

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Schuyler
Schuyler 2012-10-12
编辑： Leo Simon 2020-4-25
*NEWBIE WARNING***
I have a very basic question but couldn't find an answer after searching.
I wish to test if a multi-element cell array of strings contains a substring anywhere within the cell array's text, returning a logical true or false answer. For example, given the cell array of strings x:
x = {'qwer','asdf','zxcv'};
I wish to test if the substring 'xc' is present somewhere in x's text (true in this example).
The method I came up with is as follows:
First, concatenate the elements of the cell array of strings into a single character string, preserving the original character order:
y = char(x);
y = y';
y = y(:)'; % y now equals 'qwerasdfzxcv'
Then, test for the presence of the substring in the concatenated string:
~isempty(strfind(y,'xc')) % ans = true
~isempty(strfind(y,'123')) % ans = false
Is there a better way to do this that involves less array manipulation? Thank you for your assistance.

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采纳的回答

Sean de Wolski
Sean de Wolski 2012-10-12
matches = strfind(x,'xc');
tf = any(vertcat(matches{:}))
  2 个评论
Matt Fig
Matt Fig 2012-10-12
编辑：Matt Fig 2012-10-12
This can error if there is a different number of matches per string. For example:
x = {'qwerxc','xcaxcsdf','zxcvxcllxc'};
One could simply switch to using HORZCAT.
I would use:
tf = any(~cellfun('isempty',strfind(x,'xc')))
Schuyler
Schuyler 2012-10-14
Thank you for this clarification and for the suggestion to use HORZCAT.

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更多回答（4 个）

per isakson
per isakson 2012-10-12
编辑：per isakson 2012-10-12
Here is a construct without implicit casting of types
is_xc = not( cellfun( @isempty, strfind( x, 'xc' ) ) );
and next
any( is_xc )
Easier to read
is_xc = cellfun( @has_value, strfind( x, 'xc' ) ) );
where
function has = has_value( input )
has = not( isempty( input ) );
end
Azzi Abdelmalek
Azzi Abdelmalek 2012-10-12
编辑：Azzi Abdelmalek 2012-10-12
x = {'qwer','asdf','zxcv'};
out=any(cell2mat(cellfun(@(y) regexp(y,'xc'),x,'un',0)))
or
out=any(cell2mat(regexp(x,'xc')))
Demetrio Rodriguez Tereshkin
OP has already given, in my opinion, the best answer. Although it has to be corrected: isempty() always returns 1 for the type "cell", therefore we should use
cellfun(@isempty,strfind(y,'123'))
Schuyler
Schuyler 2012-10-12
编辑：Schuyler 2012-10-14
Wow, all three methods are great! I find:
matches = strfind(x,'xc');
tf = any(horzcat(matches{:}))
to be the simplest to visualize because it doesn't involve regular expressions or functions, but they are clearly all effective techniques. Thank you very much for the quick and helpful responses.
  1 个评论
Leo Simon
Leo Simon 2020-4-25
编辑：Leo Simon 2020-4-25
This code extends AA's answer to when you need to check if a substring of a string is contained in a cell array:
needLatexForThese = {'\bar','\ubar','\check','\hat'};
stringYes = '$\bar{x}$'
stringNo = '$x^\ast$'
f = @(s) any(cell2mat(cellfun(@(y) contains(s,y),needTexForThese,'un',0)));
f(stringYes)%returns 1
f(stringNo)%returns 0

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