Indexing arrays of varying dimensionality.

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Lionel Pöffel
Lionel Pöffel on 2 Mar 2021
Edited: Stephen23 on 23 Feb 2022
I have to handle arrays of varying dimensionality in one loop, and I have to index individual elements of those arrays.
From what I have seen in the general help, the only solution seems to be to do a stupid and unflexible switch-case-like approach, such as
sz=size(arr);
switch length(sz)
case 1:
ind1=calc_ind(1);
elem_val=arr(ind1);
case 2:
ind1=calc_ind(1);
ind2=calc_ind(2);
elem_val=arr(ind1,ind2);
case 3:
ind1=calc_ind(1);
ind1=calc_ind(2);
ind3=calc_ind(3);
elem_val=arr(ind1,ind2,ind3);
end
This makes it impossible to handle arrays of arbitrary dimensionality and is also very stupid and repetitive.
Using linear indices doesn't seem to help, because also sub2ind() needs different calls for each dimensionality.
Is there not an easier solution. like
sz=size(arr);
for d=1:length(sz)
ind_arr(d)=calc_index(d);
end
LinIndex=sub2ind(sz,ind_arr);
elem_val=arr(LinIndex);

Accepted Answer

Stephen23
Stephen23 on 2 Mar 2021
Edited: Stephen23 on 23 Feb 2022
  1 Comment
Stephen23
Stephen23 on 2 Mar 2021
Complete working example:
arr = rand(7,6,5,4,3,2);
idx = [5,3,4,4,1,1];
tmp = num2cell(idx);
x = arr(tmp{:})
x = 0.2769
y = arr(5,3,4,4,1,1)
y = 0.2769

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More Answers (1)

Lionel Pöffel
Lionel Pöffel on 3 Mar 2021
Thanks, that works beautifully!

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