Basic stratification calculations

Hi,
if I understand correctly, tapply() is your friend here,

vito

dvrecko at sfu.ca wrote:

Hi. I'm a student at SFU in Canada. The basic thing I want to do is
calculate means of different strata. I have 2 vectors. One has the 
values I
want to take the means from, the other is the four strata I am interested
in. So I essentially want to break up the information vector into the 
four
strata and calculate four means, one for each stratum. How can I do 
this in
a reasonable way?


Thanks very much.
Dean Vrecko

PS: Incidentally I forget how to see the code of functions. Does anyone
remember the command to do this?