[R-sig-eco] progamming functions help

[Stephen Cole]

Not sure if i should really post this here, but i am an ecology
student and my project is certainly ecological so........

my goal is to use R to write functions for and automate a series of
analyses i would like to do on a large data set.  The calculations are
not very difficult in themselves, however they will be very time
consuming (Plus I think R will be extremely useful and this is another
excuse to learn how to program).

I have a vector of 20 values

x <- c(20,18, 45, 16, 47, 47, 15, 26, 14,14,12,16,35,27,18,94,16,26,
26,30)

1.
I  want to select random pairs from this data set but do it without
replacement exhaustively

I know i can select random pairs without replacement using

sample(N,n,replace=F)
However i am wondering if there is any way to get 10 random pairs from
this data set without repeating any of the data points
that is to say if i got a (20, 94) for one pair, i would like to get 9
other pairs from the data without again getting 20 or 94?

2.
The second thing i would like to do is be able to select all possible
pairs of numbers and calculate each pairs variance.  I think i will
need a for loop here but I am unsure of how to do the programing.  I
am reading two books on S and s-plus now and hope they are some help.
I thought i would also post on this list and get some expert advice
for the more experienced R users

Thank-you very much

Stephen Cole
Marine Ecology Lab
Saint Francis Xavier University