How do I sort rows and get the average (mean) at the same time?

Hi, I have a 5000 X 5 matrix, which I sorted in two group: First group (2500 X 5): Pick first 5 rows (and all columns) and leave next five rows and again pick another five, leave next five and so on. Second group (2500 X 5): Pick only those which were not selected in first group. Now I need to get average of those each of picked 5 individual rows (and all columns) to make two sets of 500 X 5 matrices. Thnx in advance.

[Sean de Wolski]

A simple example with: input data, expected results, method of getting to those results is worth 10000 words.

Answer 1

[Azzi Abdelmalek]

A=rand(5000,5)
A1=zeros(500,5) % Pre-allocate
A2=A1;
ii=0;
for k=1:10:5000
ii=ii+1
  A1(ii,:)=mean(A(k:k+4,:));
  A2(ii,:)=mean(A(k+5:k+9,:));
end