non-looping way to compare cellstr arrays of different sizes

Suppose A = {'aa', 'kk', 'ccc'}, B = {'aa', 'bb', 'cc', 'dd', 'ee'}.

Is there a not-explicitly-looping way to return a logical array the same size as A that is 1 where an element of A is in B, 0 where it is not, e.g.,

"whereMember"(A,B) => [1 0 0]?

Thanks!

Answer 1

[Oleg Komarov]

A = {'aa', 'kk', 'ccc'};
B = {'aa', 'bb', 'cc', 'dd', 'ee'};

ismember(A,B)

[David Goldsmith]

DOH! (I've gotten so used to using ismember when the first argument is a scalar I forgot that it could be an array!) :-(

Thanks!

Oh, but wait a sec, I forgot: I'd also like it to be case insensitive, i.e., A = {'Aa', 'kk', 'cc'} would also return [1 0 0]. Sorry!

DG

[Oleg Komarov]

ismember(lower(A),B)

[David Goldsmith]

DOH! again. (But shouldn't that be ismember(lower(A),lower(B)) - I want it to be "commutatively" case insensitive.) :-)

Thanks one more time!

[Oleg Komarov]

Yes, then lower() both.

Answer 2

[David Goldsmith]

Here's a little function that does if the answer to the revised question is "no":

function la = cellstrIsMember(A, B, i)
  % la = 1 where the elements of cellstr array A are in cellstr array B, 0 where they are not
  % i is an optional parameter: if case matters, i=1 (the default), 
  %     0 for case-insensitive matching (which is slower)
  %
  % Author: David Goldsmith, Wash. State Dept. of Ecology, [e-mail]
  % Release date: 2011-08-24

    if nargin < 3
        i = 1;
    end

    if i || isempty(A) || isempty(B)
        la = ismember(A, B);
    else
        la = zeros(size(A));
        for i=1:length(A)
            if any(strcmpi(A{i}, B))
                la(i) = 1;
            end
        end
    end

end

[Jan]

Small suggestions: Using "numel(A)" instead of "length(A)" considers cell arrays of any dimensions.

"la=false(size(A))" replies a logical array as ISMEMBER. Then the loop can be:

for i=1:numel(A), la(i)= any(strcmpi(A{i}, B)); end

BTW.: Your loop is faster than ISMEMBER.

[Jan]

What is the meaning of your otehr thread: http://www.mathworks.com/matlabcentral/answers/13906-indexing-way-to-look-for-specifc-cell-arrays-in-a-cell-array-of-cell-arrays ???

[David Goldsmith]

Just elaborated.

[David Goldsmith]

Oh, and thanks for the refactoring--very interesting that it's faster; I guess ismember must come w/ a lot more overhead?

[Oleg Komarov]

Unfortunately yes.

[David Goldsmith]

Jan: may I credit you in my by-line comment? If yes, what is your affiliation, if any?

[Jan]

@David: I've tried to let leo.org tell me, what affiliation is. Leo meant, that either somebody adopts me, or that it concerns my fatherhood. :-) If this means my company: I'm a freelancer. Perhaps my FEX author ID 15233 is helpful?