How to index cell Matrix with a logical matrix?

Hello all, I tried to index a cell matrix with logical matrix, but it does not return me the correct output.

I want to:

Index: A ={'a','b','c','d'; 'a','b','c','d'; 'a','b','c','d'}

Matrix: B =[1,0,1,0; 0,1,1,0; 0,0,1,1]

Output: C =['a','','c',''; '','b','c',''; '','','c','d'];

I tried 'C=A(logical(B));' but without success.

Could someone help me, please?

Thank you!

[Guillaume]

Please note that

A =['a','b','c','d'; 'a','b','c','d'; 'a','b','c','d']

is not a cell array. It is a plain matrix of character and is the same as:

A = ['abcd';'abcd';'abcd'];

A cell array is:

   A = {'a','b','c','d'; 'a','b','c','d'; 'a','b','c','d'}

Note the use of curly brackets. The distinction is important for your desired output since

C =['a','','c',''; '','b','c',''; '','','c','d'];

is the same as

C = ['ac'; 'bc'; 'cd'];

[Diego Makasevicius Barbosa]

Sorry Guillaume, my fault. Actually is exactly as you said (A ={'a','b','c','d'; 'a','b','c','d'; 'a','b','c','d'}). I only typed the question incorrectly.

Answer 1

[Guillaume]

Assuming you indeed have a cell array (unlike your example):

A = {'a','b','c','d'; 'a','b','c','d'; 'a','b','c','d'}
B = logical([1,0,1,0; 0,1,1,0; 0,0,1,1]);
%option 1: create an empty cell array and use logical indexing to copy A
C = cell(size(A));
C(B) = A(B)
%option 2: copy A, and use logical indexing to replace unwanted elements 
D = A;
D(~B) = {''}

Note that for all intent and purposes '' and [] are the same, even if matlab does not display them the same

isequal(C, D) %returns true

[Diego Makasevicius Barbosa]

Guillaume, your solution works great! I don't know what I did before. Thank you !!!

[Thorsten]

No, Guillaume's solution gives you the remaining values for each row, i.e.,

 C = 
    'a'     []    'c'     []
     []    'b'    'c'     []
     []     []    'c'    'd'

or

 D = 
    'a'    ''     'c'    '' 
    ''     'b'    'c'    '' 
    ''     ''     'c'    'd'

What do you want if you are not happy with this?

[Diego Makasevicius Barbosa]

You're correct Thorsen. Guillaume's solution works fine. Thank you !

[Ahmad Suliman]

Guillaume, when I do: D(~B) = {''}, the MATLAB throws an error "Function 'subsindex' is not defined for values of class 'cell'." Could it be due to version? maybe 2016 does not support this way of indexing? Thanks,

[Florian B]

@Thorsten: Using option 2 does indeed give you an array with "empty" values (actually ' '). You can however just assign [ ] directly, which MATLAB interprets as deletion command.

%option 2: copy A, and use logical indexing to replace unwanted elements 
D = A;
D(~B) = []; % this will delete all arguments where B(i) ~= true. -> before: {''}

This question - solving the problem for a 2D-cell array - may also help. A full alternative to the snippet above would be:

% copy A, and use logical indexing to replace unwanted {elements} with {''}
D = A;
D(~B) = {''};

% Identify empty cells
idx = cellfun(@isempty, D);
% Delete rows with empty cell
D(~any(idx)) = [];

Answer 2

[Thorsten]

Not exactly want you want, but close:

 C = A;
 C(B ~= 1) = ' '

[Diego Makasevicius Barbosa]

Thorsen, The problem of this solution is that the output is the follow array:

C= {'a' 'b' 'c' 'c' 'c' 'd'}

And I need to know which is the remaining values for each row.

Thank you!!