Is the following what you want?
> a <- c(1,2,3,4,4,4,5,5)
> b <- c(11,7,4,9,8,3,12,4)
> split(b, a)
$1
[1] 11
$2
[1] 7
$3
[1] 4
$4
[1] 9 8 3
$5
[1] 12 4
Note that your df<-cbind(a,b) produces a matrix, not the data.frame
that your df suggests you want. Use df<-data.frame(a,b) to make
a data.frame. Then you could do with(df, split(a,b)) to operate on
the a and b in the data.frame df.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf
> Of Marco Guerzoni
> Sent: Tuesday, March 13, 2012 10:51 AM
> To: r-help at r-project.org
> Subject: [R] reshaping a dataset for a network
>
> dear all,
> apologizes for bothering with a probably stupid question but I really
> don' t know how to proceed.
>
> I have a dataset which look like df
>
> a <- c(1,2,3,4,4,4,5,5)
> b <- c(11,7,4,9,8,3,12,4)
> df <-cbind(a,b)
>
> I would like to have one which looks like this:
>
> a
> 1 11
> 2 7
> 3 4
> 4 9 8 3
> 5 12 4
>
> a are vertex of a network, b the edges. In the data the lenght of a is
> about 50000
>
> I read several posts about reshape, reshape2, split, ldply but I
> couldn't manage to do it. The problem seems to be that the is not a
real
> panel.
>
> Any help would be really appreciated,
> my best regards
> Marco
>
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