Loop For extract maximum rows of matrix based on vectors

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

[Walter Roberson]

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 ?

Answer 1

[Voss]

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

Answer 2

[Fangjun Jiang]

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