How to index cell Matrix with a logical matrix?
11 visualizaciones (últimos 30 días)
Mostrar comentarios más antiguos
Diego Makasevicius Barbosa
el 26 de Nov. de 2015
Comentada: Florian B
el 24 de Feb. de 2022
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!
2 comentarios
Guillaume
el 26 de Nov. de 2015
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'];
Respuesta aceptada
Guillaume
el 26 de Nov. de 2015
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
5 comentarios
Ahmad Suliman
el 30 de Jul. de 2017
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
el 24 de Feb. de 2022
@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)) = [];
Ver también
Categorías
Más información sobre Matrix Indexing en Help Center y File Exchange.
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!