Creating Matrix Subset automatic.

I have a matrix, A which have a 9 row and 9 column. I need to make a subset from it.

The prospective subset we need : S1= [ 1 4 7] ; S2 =[2 5 8]; S3= [3 6 9]

Here S1 is telling that I need matrix that will take the element of 1st, 4th, 7th row of the matrix A and by doing vertical concatenation the matrix is perfectly formed.

I did like following which works perfect but I am wondering if my matrix is very large then is there any alternating way to that ? something like usiing some loops?

% Creating Matrix Subset

A=randi(9,9);

S1_a= A(1,:);

S1_b= A(4,:);

S1_c= A(7,:);

S1 = [S1_a; S1_b; S1_c] ; % Vertically concatenate

Answer 1

[Matt J]

You should be doing it as follows:

S=A([1,4,7],:);

[Walter Roberson]

A(2:3:end, :)