How to delete max values for every 5 rows

I want to delete the max value for column 1 for every 5 rows with idx column 2

The matrix

A =

1 1

2 2

6 3

12 2

4 5

9 6

14 1

5 1

6 9

8 10

11 11

12 3

9 13

4 6

10 15

the result will be

1 1

2 2

6 3

4 5

9 6

5 1

6 9

8 10

11 11

9 13

4 6

10 15

Answer 1

[Voss]

A = [
     1     1
     2     2
     6     3
    12     2
     4     5
     9     6
    14     1
     5     1
     6     9
     8    10
    11    11
    12    3
     9    13
     4    6
    10    15];

% group size
n = 5;

% index of max value, within each group of n (5)
[~,idx] = max(reshape(A(:,1),n,[]),[],1)

idx = 1×3

4 2 2

% convert to index in A
rows_to_delete = (0:numel(idx)-1)*n+idx

rows_to_delete = 1×3

4 7 12

% delete the rows of A
A(rows_to_delete,:) = []

A = 12×2

1 1 2 2 6 3 4 5 9 6 5 1 6 9 8 10 11 11 9 13