Accessing cell array entries using arrays

Question

OK 2024-7-1，9:05

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2133391-accessing-cell-array-entries-using-arrays

评论： OK 2024-7-1，9:35

I have a multi-dimensional cell array and matrix, whose columns correspons to indices of the cell array. I want to populate the cells with arrays that correspond to the indices of the columns that refer to the given cell.

Minimal example:

A=cell(2,2);
B=[1 2 2 1 1; 2 1 2 1 2]
B = 2x5
     1     2     2     1     1
     2     1     2     1     2
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A{1,1}=[4];
A{1,2}=[1,5];
A{2,1}=[2];
A{2,2}=[3]
A = 2x2 cell array
    {[4]}    {[1 5]}
    {[2]}    {[  3]}

I'm trying to do this automatically by looping over the columns of the matrix B, but I can't figure out how to extract the entries of the array without keeping the array form. Calling neither

A(B(:,1)) 
ans = 2x1 cell array
    {[4]}
    {[2]}

nor

A{B(:,1)}
ans = 4
ans = 2

produces the correct entry

A{1,2}
ans = 1x2
     1     5
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Answer 1

Stephen23 2024-7-1，9:12

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编辑：Stephen23 2024-7-1，9:13

在 MATLAB Online 中打开

B = [1,2,2,1,1; 2,1,2,1,2];
V = 1:size(B,2);
A = accumarray(B.',V(:),[],@(m){m.'})
A = 2x2 cell array
    {[4]}    {[1 5]}
    {[2]}    {[  3]}
A{1,2}
ans = 1x2
     1     5
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OK 2024-7-1，9:15

Thank you!

Stephen23 2024-7-1，9:25

编辑：Stephen23 2024-7-1，9:29

在 MATLAB Online 中打开

If you really want to use a loop:

A = cell(2,2);
B = [1,2,2,1,1; 2,1,2,1,2];
for k = 1:size(B,2)
    C = num2cell(B(:,k));
    A{C{:}} = [A{C{:}},k];
end
A
A = 2x2 cell array
    {[4]}    {[1 5]}
    {[2]}    {[  3]}

Or:

A = cell(2,2);
for k = 1:size(B,2)
    A{B(1,k),B(2,k)} = [A{B(1,k),B(2,k)},k];
end
A
A = 2x2 cell array
    {[4]}    {[1 5]}
    {[2]}    {[  3]}

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Answer 2

Aquatris 2024-7-1，9:21

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2133391-accessing-cell-array-entries-using-arrays#answer_1479166

在 MATLAB Online 中打开

I think you want to use B columns as indeces to extract info from A, so:

A=cell(2,2);
B=[1 2 2 1 1; 
   2 1 2 1 2]
B = 2x5
     1     2     2     1     1
     2     1     2     1     2
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A{1,1}=[4];
A{1,2}=[1,5];
A{2,1}=[2];
A{2,2}=[3];
for i = 1:size(B,2)
    fprintf('The B(:,%d)= [%d, %d]'' and A(B(:,%d)'') is: ',i,B(:,i),i)
    disp(A{B(1,i),B(2,i)})
end
The B(:,1)= [1, 2]' and A(B(:,1)') is: 
     1     5
The B(:,2)= [2, 1]' and A(B(:,2)') is: 
     2
The B(:,3)= [2, 2]' and A(B(:,3)') is: 
     3
The B(:,4)= [1, 1]' and A(B(:,4)') is: 
     4
The B(:,5)= [1, 2]' and A(B(:,5)') is: 
     1     5