try this:

> x <- read.table(textConnection("     id group
+   1   1     1
+   2   2     1
+   3   3     1
+   4   4     1
+   5   5     2
+   6   6     2
+   7   7     3
+   8   8     3
+   9   9     3
+   10 10     3
+   11 11     3
+   12 12     3"), header=TRUE)
> # split by group and process
> result <- lapply(split(x, x$group), function(i){
+     # create combinations
+     com <- combn(i$id, length(i$id) - 1L)
+     t(apply(com, 2, function(.col){
+         c(setdiff(i$id, .col), i$group[1L], .col)
+     }))
+ })
> # determine maximum number of column
> col.max <- max(sapply(result, ncol))
> # now create output with proper number of columns
> output <- do.call(rbind, lapply(result, function(.grp){
+     while (ncol(.grp) < col.max) .grp <- cbind(.grp, NA)
+     .grp
+ }))
>
> # add column names
> colnames(output) <- c('id', 'group', paste('gm', seq(col.max - 2),
sep=''))
> output
      id group gm1 gm2 gm3 gm4 gm5
 [1,]  4     1   1   2   3  NA  NA
 [2,]  3     1   1   2   4  NA  NA
 [3,]  2     1   1   3   4  NA  NA
 [4,]  1     1   2   3   4  NA  NA
 [5,]  6     2   5  NA  NA  NA  NA
 [6,]  5     2   6  NA  NA  NA  NA
 [7,] 12     3   7   8   9  10  11
 [8,] 11     3   7   8   9  10  12
 [9,] 10     3   7   8   9  11  12
[10,]  9     3   7   8  10  11  12
[11,]  8     3   7   9  10  11  12
[12,]  7     3   8   9  10  11  12
>


On Tue, Apr 13, 2010 at 8:04 AM, Duijvesteijn, Naomi <
Naomi.Duijvesteijn@ipg.nl> wrote:

>
>   Hi all,
>
>
>
>   I  want  to  make  extra  columns in my datafile where the id of every
>   groupmember is mentioned in separate columns. To explain it better see
> the
>   example:
>
>
>
>   id<-c(1,2,3,4,5,6,7,8,9,10,11,12)
>
>   group<-c(1,1,1,1,2,2,3,3,3,3,3,3)
>
>   a<-as.data.frame(cbind(id,group))
>
>   a
>
>      id group
>
>   1   1     1
>
>   2   2     1
>
>   3   3     1
>
>   4   4     1
>
>   5   5     2
>
>   6   6     2
>
>   7   7     3
>
>   8   8     3
>
>   9   9     3
>
>   10 10     3
>
>   11 11     3
>
>   12 12     3
>
>
>
>   Result should be (gm = groupmember)
>
>
>   id  group   gm1         gm2       gm3      gm4           gm5       gm6
>     gm7            etc.
>
>   1     1          2             3           4          NA            NA
>   NA            NA
>
>   2     1          1             3           4          NA            NA
>   NA            NA
>
>   3     1          1             2           4          NA            NA
>   NA            NA
>
>   4     1          1             2           3          NA            NA
>   NA            NA
>
>   5     2          6             NA          NA        NA             NA
>   NA            NA
>
>   6     2          5             NA          NA        NA             NA
>   NA            NA
>
>   7     3          8            9           10          11            12
>     NA             NA
>
>   8        3            7               9              10             11
>   12          NA             NA
>
>   9        3            7               8              10             11
>   12          NA             NA
>
>   10       3            7               8              9              11
>   12          NA             NA
>
>   11       3            7               8              9              10
>   12          NA             NA
>
>   12       3            7               8              9              10
>   11          NA             NA
>
>
>
>   What I have been trying so far is reshape, but this doesn’t put the id’s
> of
>   the groupmembers of different groups under the same columnname. It makes
> new
>   columnnames per group.
>
>
>   Couls somebody help me out with this? I really appreciate it
>
>
>   Regards,
>
>   Naomi Duijvesteijn
>
>
>
>
>   Disclaimer:  De  informatie opgenomen in dit bericht (en bijlagen) kan
>   vertrouwelijk zijn en is uitsluitend bestemd voor de geadresseerde(n).
>   Indien u dit bericht ten onrechte ontvangt, wordt u geacht de inhoud niet
> te
>   gebruiken, de afzender direct te informeren en het bericht te
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>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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