Find subscripts in a 3D matrix
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I have a 3D matrix, called A, and I want to find the subscripts for all places where elements of vector B appear. The elements of B apper more than one time in the matrix A.
I tried it using function subs to obtain directly the susbsripts, but I obtained a result where many page numbers are wrong (it shows a higher number (5) than the existing pages (3)). Bellow the code:
A(:,:,1)=[1 2 ; 3 3 ; 5 7 ; 4 2];
A(:,:,2)=[9 1 ; 4 4 ; 9 2 ; 4 6];
A(:,:,3)=[2 4 ; 7 4 ; 3 1 ; 6 4];
B = [9 4 1];
[row,col,page] = ind2sub(size(A),find(A(:)==B))
Also I tried using function find to obtain the linear indexes to later convert them to subscripts; however, I only obtain the first place were the element is placed on the matrix:
n = arrayfun(@(x) find(A==x,1),B);
[row, col, page] = ind2sub(size(A), n);
采纳的回答
A(:,:,1)=[1 2 ; 3 3 ; 5 7 ; 4 2];
A(:,:,2)=[9 1 ; 4 4 ; 9 2 ; 4 6];
A(:,:,3)=[2 4 ; 7 4 ; 3 1 ; 6 4];
B = [9 4 1];
[row,col,page] = ind2sub(size(A),find(ismember(A,B)))
4 个评论
Walter Roberson
2021-1-28
Your error is that A(:) == B is numel(A) by length(B). The first column each element of A to the first element of B; the second column compares each element of A to the second element of B, and so on.
Another way you could do it is
[row,col,page] = ind2sub(size(A),find(any(A(:)==B,2)))
Fernando Montero
2021-1-28
Walter Roberson
2021-1-28
find(ismember(A,B)) would be linear
sub2ind(size(A), row,col,page)
if you need to reconstruct linear
Fernando Montero
2021-1-28
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