Take lines from array

I have an 64X4 array A , and I want take out every first 2 lines in every 4 line, is there some easy way to do that?

Answer 1

[Stephan]

A = repmat([1 1 1 1; 2 2 2 2; 3 3 3 3; 4 4 4 4],16,1); % Example matrix
B = zeros(32,4); % Preallocate B
B(1:2:end) = A(1:4:end,:); % Take line 1 of every 4.th line in A
B(2:2:end) = A(2:4:end,:); % Take line 2 of every 4.th line in A

results in:

A =

     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4
     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4


B =

     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2
     1     1     1     1
     2     2     2     2

[j shen]

Thank you!

Answer 2

[KSSV]

A = rand(64,2) ;
B = reshape(A',2,4,[]) ;
B = permute(B,[2 1 3]) ;
iwant = B(1:2,:,:) ;