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r: LEXICOGRAPHIC ORDERING

3 messages · Clark Allan, Uwe Ligges, Dimitris Rizopoulos

Clark Allan
# 
HI all

i have a seemingly simple question.

given a sequence of numbers say, 1,2,3,4,5.

i would like to get all of the possible two number arrangments
(combinations), all 3 number arrangents ... 5 number arrangements
(combinations).

i.e. 

in the 2 number case:

12,13,14,15,23,24,25,34,35,45



any ideas?
Uwe Ligges
#
Clark Allan wrote:
library(gtools)
   combinations(5, 2) %*% c(10, 1)

Uwe Ligges
Dimitris Rizopoulos
# 
here is a possible solution:

subsets <- function (n, r, s = 1:n) {
    # from V&Rs (2000) S Programming, Springer, p.49
    if (mode(n) != "numeric" || length(n) != 1 || n < 1 || (n%%1) != 
0) stop("bad value of n")
    if (mode(r) != "numeric" || length(r) != 1 || r < 1 || (r%%1) != 
0) stop("bad value of r")
    if (!is.atomic(s) || length(s) < n) stop("s is either non-atomic 
or too short")
    fun <- function(n, r, s)
        if (r <= 0) vector(mode(s), 0)
        else if (r >= n) s[1:n]
        else rbind(cbind(s[1], Recall(n - 1, r - 1, s[-1])), 
Recall(n - 1, r, s[-1]))
    fun(n, r, s)
}
##############
x <- c(1, 3, 5, 7, 9)

ind <- subsets(length(x), 2)
apply(matrix(x[ind], nc = ncol(ind)), 1, function(x) 
as.numeric(paste(x, collapse = "")))

ind <- subsets(length(x), 3)
apply(matrix(x[ind], nc = ncol(ind)), 1, function(x) 
as.numeric(paste(x, collapse = "")))



I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Clark Allan" <Allan at stats.uct.ac.za>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, May 27, 2005 3:24 PM
Subject: [R] r: LEXICOGRAPHIC ORDERING
--------------------------------------------------------------------------------