Actually, (now that I know about combn), a better way is t(matrix(set[combn(7,2)], nrow = 2))
Bill V. -----Original Message----- From: Adrian Dusa [mailto:[EMAIL PROTECTED] Sent: Thursday, 15 November 2007 11:55 PM To: Venables, Bill (CMIS, Cleveland) Cc: [EMAIL PROTECTED]; r-help@r-project.org Subject: Re: [R] generate combination set Using your "set", wouldn't it be simpler like this? t(apply(combn(7,2), 2, function(x) set[x])) Hth, Adrian On Thursday 15 November 2007, [EMAIL PROTECTED] wrote: > There are a number of packages that do this, but here is a simple > function for choosing subsets: > > subsets <- function(n, r) { > if(is.numeric(n) & length(n) == 1) v <- 1:n else { > v <- n > n <- length(v) > } > subs <- function(n, r, v) > if(r <= 0) NULL else > if(r >= n) matrix(v[1:n], nrow = 1) else > rbind(cbind(v[1], subs(n - 1, r - 1, v[-1])), > subs(n - 1, r , v[-1])) > subs(n, r, v) > } > > Here is an example of how to use it: > > set <- LETTERS[1:7] > > subsets(set, 2) > > [,1] [,2] > [1,] "A" "B" > [2,] "A" "C" > [3,] "A" "D" > [4,] "A" "E" > [5,] "A" "F" > [6,] "A" "G" > [7,] "B" "C" > [8,] "B" "D" > [9,] "B" "E" > [10,] "B" "F" > [11,] "B" "G" > [12,] "C" "D" > [13,] "C" "E" > [14,] "C" "F" > [15,] "C" "G" > [16,] "D" "E" > [17,] "D" "F" > [18,] "D" "G" > [19,] "E" "F" > [20,] "E" "G" > [21,] "F" "G" > > > Bill Venables > CSIRO Laboratories > PO Box 120, Cleveland, 4163 > AUSTRALIA > Office Phone (email preferred): +61 7 3826 7251 > Fax (if absolutely necessary): +61 7 3826 7304 > Mobile: +61 4 8819 4402 > Home Phone: +61 7 3286 7700 > mailto:[EMAIL PROTECTED] > http://www.cmis.csiro.au/bill.venables/ > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On Behalf Of [EMAIL PROTECTED] > Sent: Thursday, 15 November 2007 2:51 PM > To: r-help@r-project.org > Subject: [R] generate combination set > > I have a set data={A,B,C,D,E,F,G} > I want to choose 2 letter from 8 letters, i.e. generate the combination > set > for choose 2 letters from 8 letters. > I want to get the liking: > combination set={AB,AC,AD,....} > Does anyone konw how to do in R. > > thanks, > > Aimin > > ______________________________________________ > 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. -- Adrian Dusa Romanian Social Data Archive 1, Schitu Magureanu Bd 050025 Bucharest sector 5 Romania Tel./Fax: +40 21 3126618 \ +40 21 3120210 / int.101 ______________________________________________ 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.
