[R] things that are difficult/impossible to do in SAS or SPSS but simple in R

[Jeffrey J. Hallman]

SAS has no facilities for date arithmetic and no easy way to build it
yourself.  In fact, that's the biggest problem with SAS: it stinks as a
programming environment, so it's always much more difficult than it should be
to do something new.  As soon as you get away from the canned procs and have
to write something of your own, SAS falls down.

I don't know enough about SPSS to comment.
-- 
Jeff