[R] Sorting a dataframe

[Paul, David A]

Undoubtedly a simple question:

I've looked at order() and sort() in the help pages for
R1.7.1.  It doesn't appear that these functions are immediately
suited to doing the same thing as

PROC SORT DATA = BLAH;
	BY X Y Z;
RUN;

in SAS.  I have also checked Frank Harrell's Hmisc library.
Could someone point me in the right direction so I can sort 
by the levels of Z within the levels of Y within the levels 
of X?  Everything needs to be in ascending order.


Much thanks in advance,
  david paul