permutation

The gregmisc package contains a function 'perumutations' which generates all
permutations of n choose r.  It also contains 'combinations' which generates
all combinations, and which appears to match your example:

library(gregmisc)

Loading required package: MASS

Attaching package `gregmisc':


        The following object(s) are masked from package:base :

         lowess

permutations(n=4,r=4)

      [,1] [,2] [,3]
 [1,]    1    2    3
 [2,]    1    2    4
 [3,]    1    3    2
 [4,]    1    3    4
 [5,]    1    4    2
 [6,]    1    4    3
 [7,]    2    1    3
 [8,]    2    1    4
 [9,]    2    3    1
[10,]    2    3    4
[11,]    2    4    1
[12,]    2    4    3
[13,]    3    1    2
[14,]    3    1    4
[15,]    3    2    1
[16,]    3    2    4
[17,]    3    4    1
[18,]    3    4    2
[19,]    4    1    2
[20,]    4    1    3
[21,]    4    2    1
[22,]    4    2    3
[23,]    4    3    1
[24,]    4    3    2

combinations(n=4,r=3)

     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    1    2    4
[3,]    1    3    4
[4,]    2    3    4

See the help pages for details.

-Greg

-----Original Message-----
From: Pauline Gu [mailto:gu4 at llnl.gov]
Sent: Monday, November 25, 2002 7:55 PM
To: r-help at stat.math.ethz.ch
Subject: [R] permutation


Dear R experts,

Is there any function in R that I can calculate the
permutation lists?  I
would like to know if there is any generic one for finding all the
permutation of n choose k?

For example:

perms <- list(1:2)
perms <- add.ttt(3:4, perms)
should give me

 > perms

[[1]]
[1] 3 4 1 2

[[2]]
[1] 3 1 4 2

[[3]]
[1] 3 1 2 4

and perms <- add.ttt(5:6, perms)
should give me:
[[1]]
[1] 5 6 3 4 1 2

[[2]]
[1] 5 3 6 4 1 2

[[3]]
[1] 5 3 4 6 1 2

[[4]]
[1] 5 3 4 1 6 2

[[5]]
[1] 5 3 4 1 2 6

[[6]]
[1] 5 6 3 1 4 2

[[7]]
[1] 5 3 6 1 4 2

[[8]]
[1] 5 3 1 6 4 2

[[9]]
[1] 5 3 1 4 6 2

[[10]]
[1] 5 3 1 4 2 6

[[11]]
[1] 5 6 3 1 2 4

[[12]]
[1] 5 3 6 1 2 4

[[13]]
[1] 5 3 1 6 2 4

[[14]]
[1] 5 3 1 2 6 4

[[15]]
[1] 5 3 1 2 4 6


This example is just for those with k=2.  How would I
calculate those for
any k?

Thanks in advance for your help.

Pauline

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