how I can make the matrix?

[Star Strider]

I see no consistent relationship that could be coded as any sort of ‘rule’ as to what rows of 'A’ become ‘B’.

.

Answer 1

[the cyclist]

I think this does what you want. (It produces the correct output for your example.)

If not, I hope you can understand and adjust the logic.

A = [2    10  ;
     2.5   8.9;
     2.5   9  ;
     2.65  9  ;
     3     7  ;
     3     8  ;
     4     7.5;
     4.5   4.9];

B = A;
idx = 2;

while idx < size(B,1)
    if B(idx,1) >= B(idx-1,1) && B(idx-1,2) > B(idx,2)
        idx = idx+1;
    else
        B(idx,:) = [];
    end
end

B

B = 4×2

2.0000 10.0000 2.5000 8.9000 3.0000 7.0000 4.5000 4.9000