suppose to have the following dataset:

data dataset;
  input week_number Var1 Var2;
cards;
1  55  98
2  34  34
3  21  0
4  76  12
5  98  0
.. ... ..
52 21  43
;run;

what is the best way to calculate and add the following: lag of -1 week; lag of +1 week; lag of -2 weeks; lag of +2 weeks to the original dataset?

Thank you in advance