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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED] > -- Erin Hodgess Associate Professor Department of Computer and Mathematical Sciences University of Houston - Downtown mailto: [EMAIL PROTECTED] ______________________________________________ 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.
