How to get the smallest value in submatrices

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Hung Dao
Hung Dao 2021-10-2
评论： Hung Dao 2021-10-2
Hi,
I would appreciate if you could help me with this problem.
I have a big matrix , where are submatrices of the same size.
I want to get a vector containing the smallest elements in each submatrices. I want to avoid for loop as it might slow down my whole program.
Thanks.

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采纳的回答

Bruno Luong
Bruno Luong 2021-10-2
Ran in:
B=randi(9,10,2)
B = 10×2
3 7 6 6 6 3 3 5 3 9 3 5 1 5 5 9 8 2 7 8
[m,n] = size(B);
k = 5;
if mod(m,k)
error('m must divisible by k');
end
minsub = min(reshape(B,[m/k k n]),[],[1 3]).'
minsub = 5×1
3 3 3 1 2

更多回答（1 个）

Kevin Holly
Kevin Holly 2021-10-2
cellfun(@min,B,'UniformOutput',false)
%or
cellfun(@min,cellfun(@min,B,'UniformOutput',false),'UniformOutput',false)
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Kevin Holly
Kevin Holly 2021-10-2
I was under the impression that you already had a big matrix B that contained submatrices. If this is not the case, how are your data organized? Are all the matrices in a folder/workspace individually?
Hung Dao
Hung Dao 2021-10-2
My apologies for the confusion.
My algorithm leads to a big matrix, not the submatrices.
But I need to partition the big matrix into submatrices of the same size, and in each submatrix I want to find the minimum value.
I hope it is clear now.
Thank you.

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