vector handles

[george.brida]

Hi all,
suppose that we have the following vector u=[10 11 12 14 15 14 10 11 12 14 15 17 20 21 20 23]' of length 16. I would like to create  the following vectors:
u_1 composed by the elements number 1, 5, 9 and 13 of u
u_2 composed by the elements number 2, 6, 10 and 14 of u
u_3 composed by the elements number 3, 7, 11 and 15 of u
u_4 composed by the elements number 4, 8, 12 and 16 of u
can you help me with a program performing this task. Thank you very much in advance.
George.