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Indexing Array Elements Using Row Number Stored in another Matrix

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Ben
Ben 2020-8-26
评论： Ben 2020-8-27
This seems like it should be a fairly simple common thing to do and Yet I cannot find any similar questions or information anywhere on the forums. Basically, all I want to do is index values in a matrix using the numbers stored in another Matix. For example if I have a Matrix A
A = [5 14 24 5; 16 12 22 15; 8 55 44 21; 3 2 34 65]
and a Matix B
B = [1; 2; 4; 3]
The numbers contained in B correspond to row numbers that need to be accessed in A. In otherwords I would like to access the values in the following locations of matrix A (1,1), (2,2), (4,3), (3,4). I would then like to store these values in a new Matrix. So in this instance, the output contained in that new Matrix would be 5 12 34 21
I tried the following:
A = [5 14 24 5; 16 12 22 15; 8 55 44 21; 3 2 34 65];
B = [1; 2; 4; 3];
for i = 1:4
z = B(1,i)
Y(i) = A(z,i)
end

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采纳的回答

madhan ravi
madhan ravi 2020-8-26
编辑：madhan ravi 2020-8-26
Wanted = A(sub2ind(size(A), B, (1:numel(B)).'))
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Stephen23
Stephen23 2020-8-27
>> A = [5,14,24,5;16,12,22,15;8,55,44,21;3,2,34,65];
>> B = [1;2;4;3]; % row subscript indices
>> C = 1:numel(B); % column subscript indices
>> X = sub2ind(size(A),B(:),C(:)); % linear indices
>> Y = A(X)
Y =
5
12
34
21

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