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Extracting elements from one matrix and placing in another

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Brian DeCicco
Brian DeCicco on 16 Jun 2021
Commented: Brian DeCicco on 16 Jun 2021
Hello,
I have a matrix of size 97x97x117 (called yearly_array2). I'm trying to extract specific portions of the 3rd dimension (i.e. positions 7, 10, 34, 52, 79, 82, 88, 94, 100, & 115) and place those in a brand new matrix (called SLP_top_10). The expected size of the new matrix should be 1440x721x10. When I run the loop in my code, each iteration of "i" gets replaced by the next, and I'm left with the last postion (when i = 115) in the new matrix, when instead I want all 10 postions within my new matrix. What can I do, or how should I modify the following code, to retain all 10 positions of interest in my new array?
SLP_top_10 = zeros(97,97,10); %pre-allocating array of expected size
for i = [7 10 34 52 79 82 88 94 100 115] %positions of interest from yearly_array2
SLP_top_10 = yearly_array2(:,:,i);
end

Accepted Answer

Chunru
Chunru on 16 Jun 2021
Edited: Chunru on 16 Jun 2021
The following will do.
i = [7 10 34 52 79 82 88 94 100 115] %posi
SLP_top_10 = yearly_array2(:,:,i);
  1 Comment
Brian DeCicco
Brian DeCicco on 16 Jun 2021
Thank you Chunru, it works now! That was really helpful...sometimes I try to overcomplicate things by creating loops when I don't have to.

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More Answers (2)

dpb
dpb on 16 Jun 2021
MATLAB assigns the complete array to the LHS without having used subscrpting to indicate you want to place each plane extracted into a given new plane in the output array.
But, MATLAB also uses vector addressing so you "don't need no steenkin' loops!" at all.
iTop10 = [7 10 34 52 79 82 88 94 100 115];
SLP_top_10 = yearly_array2(:,:,iTop10);

David Hill
David Hill on 16 Jun 2021
I am confused when you said the expected size was 1440x721x10 but then your code has the corrected expected size.
SLP_top_10=yearly_array2(:,:,[7 10 34 52 79 82 88 94 100 115]);%expected size 97x97x10
  1 Comment
Brian DeCicco
Brian DeCicco on 16 Jun 2021
Yeah sorry, I miss-typed earlier...the first 2 dimesnions should have been 97x97.

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