# Accessing cell array entries using arrays

1 vue (au cours des 30 derniers jours)
OK le 1 Juil 2024
Commenté : OK le 1 Juil 2024
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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### Réponse acceptée

Stephen23 le 1 Juil 2024
Modifié(e) : Stephen23 le 1 Juil 2024
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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##### 2 commentairesAfficher AucuneMasquer Aucune
OK le 1 Juil 2024
Thank you!
Stephen23 le 1 Juil 2024
Modifié(e) : Stephen23 le 1 Juil 2024
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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### Plus de réponses (1)

Aquatris le 1 Juil 2024
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
##### 1 commentaireAfficher -1 commentaires plus anciensMasquer -1 commentaires plus anciens
OK le 1 Juil 2024
Thank you! I actually wanted to populate A using the column indices from B (as was resolved in the accepted answer)

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