Loop For extract maximum rows of matrix based on vectors

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abdullah al-dulaimi
回答： Fangjun Jiang 2022-12-7
I have this data , Consist of 3 vectors, i want to create a Loop for 1:5: size(data) , to extract rows that have maximum value for vector 2 (colomn number 2)
1 3 4
1 5 4
1 6 4
1 2 4
1 1 4
2 4 4
2 4 4
2 4 4
2 4 4
2 5 4
1 1 4
1 1 4
1 2 4
1 3 4
1 5 4
2 5 4
2 5 4
2 5 4
2 5 4
2 6 4
The result will be
1 6 4
2 5 4
1 5 4
2 6 4
  1 个评论
Walter Roberson
Walter Roberson 2022-12-7
Is the rule that you want to find the maximum for each group of lines that has the same value in the first column? Even if the third column is different? Or should it be groups of lines that have the same first and third column ?

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采纳的回答

Voss
Voss 2022-12-7
Ran in:
data = [
1 3 4
1 5 4
1 6 4
1 2 4
1 1 4
2 4 4
2 4 4
2 4 4
2 4 4
2 5 4
1 1 4
1 1 4
1 2 4
1 3 4
1 5 4
2 5 4
2 5 4
2 5 4
2 5 4
2 6 4
];
[n_rows,n_cols] = size(data);
assert(mod(n_rows,5) == 0)
result = zeros(n_rows/5,n_cols);
for ii = 1:5:n_rows-4
temp_data = data(ii+(0:4),:);
[~,idx] = max(temp_data(:,2));
result((ii-1)/5+1,:) = temp_data(idx,:);
end
disp(result);
1 6 4 2 5 4 1 5 4 2 6 4

更多回答（1 个）

Fangjun Jiang
Fangjun Jiang 2022-12-7
Ran in:
a=[1 3 4
1 5 4
1 6 4
1 2 4
1 1 4
2 4 4
2 4 4
2 4 4
2 4 4
2 5 4
1 1 4
1 1 4
1 2 4
1 3 4
1 5 4
2 5 4
2 5 4
2 5 4
2 5 4
2 6 4];
b=reshape(a',3,5,[])
b =
b(:,:,1) = 1 1 1 1 1 3 5 6 2 1 4 4 4 4 4 b(:,:,2) = 2 2 2 2 2 4 4 4 4 5 4 4 4 4 4 b(:,:,3) = 1 1 1 1 1 1 1 2 3 5 4 4 4 4 4 b(:,:,4) = 2 2 2 2 2 5 5 5 5 6 4 4 4 4 4
c=transpose(squeeze(max(b,[],2)))
c = 4×3
1 6 4 2 5 4 1 5 4 2 6 4

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