Thank- you all for you suggestions and help.  I have now resolved my
issue.   This help forum is one of the things that makes R a great platform
for statistics.

Stephen Cole
Marine Ecology Lab
Saint Francis Xavier University

On Wed, Oct 8, 2008 at 8:07 AM, Erin Hodgess <erinm.hodgess@gmail.com>wrote:

> Actually, you will have duplicates with 400 pairs.
>
> Here you will have 13^2 pairs with replacement and 13*12 pairs without
> replacement and with regard to order.
> How about this:
> > z <- unique(x)
> > y <- expand.grid(z[1:13],z[1:13])
> > xx <- y[,1] != y[,2]
> > y[xx,]
>
> Just another thought.
>
> Erin
>
>
> On Wed, Oct 8, 2008 at 5:55 AM, Erin Hodgess <erinm.hodgess@gmail.com>
> wrote:
> > For all possible pairs, you'll have 20^2 pairs.
> > This is a way to do it:
> >
> > expand.grid(x[1:20],x[1:20])
> >
> > HTH,
> > Erin
> >
> >
> > On Wed, Oct 8, 2008 at 4:43 AM, Jim Lemon <jim@bitwrit.com.au> wrote:
> >> Stephen Cole wrote:
> >>>
> >>> ...
> >>> 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
> >>>
> >>
> >> matrix(x[sample(1:20,20)],nrow=2)
> >>
> >> then step through the columns of the resulting matrix
> >>>
> >>> 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 you want to use the combn function, but you are going to get a
> lot
> >> of pairs...
> >>
> >> Jim
> >>
> >> ______________________________________________
> >> R-help@r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> >
> >
> > --
> > Erin Hodgess
> > Associate Professor
> > Department of Computer and Mathematical Sciences
> > University of Houston - Downtown
> > mailto: erinm.hodgess@gmail.com
> >
>
>
>
> --
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess@gmail.com
>

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