[R] Re-sort list of vectors

[Adaikalavan Ramasamy]

Here is one possible and ugly hack. 

 mylist  <- list("1"=c(a=1, b=2, c=3), "2"=c(d=4, b=5, e=6))

 myvec   <- unlist( mylist )
   1.a 1.b 1.c 2.d 2.b 2.e 
     1   2   3   4   5   6 
 
 mymat   <- sapply( strsplit( names(myvec) , split="\\." ) , c )
      [,1] [,2] [,3] [,4] [,5] [,6]
  [1,] "1"  "1"  "1"  "2"  "2"  "2" 
  [2,] "a"  "b"  "c"  "d"  "b"  "e" 


 tmp     <- data.frame( "main"=mymat[2,], 
                        "sub"=mymat[ 1,], "value"=myvec )
     main sub value
 1.a    a   1     1
 1.b    b   1     2
 1.c    c   1     3
 2.d    d   2     4
 2.b    b   2     5
 2.e    e   2     6

I would be quite happy with at this point to loop through the rows and
insert this element by element into MySQL. This may be inefficient for
large datasets. Otherwise I can create this into a matrix with NAs.


So here is my ugly hack to get the list format that you desire. 

 tmp2    <- data.frame( "main"=tmp$main, 
              "elements"=paste('"', tmp$sub, '"=', tmp$value, sep="") )

 newlist <- tapply( noquote(as.character(tmp2$elements)), tmp2$main, c )

 newlist
 $a
 [1] "1"=1

 $b
 [1] "1"=2 "2"=5

 $c
 [1] "1"=3

 $d
 [1] "2"=4

 $e
 [1] "2"=6

I am sure someone will come up with a shorter and neater solution.

Regards, Adai



On Mon, 2005-08-15 at 19:09 +0200, Jan Hummel wrote:
>  Thanks a lot! But unfortunately I will not know the dimensions of both lists. And further, the lists may be (partly) disjoint as: x <- list("1"=c(a=1, b=2, c=3), "2"=c(d=4, b=5, e=6)). And last but not least I'm really have to have access to the names of the named list items.
> 
> The problem I dealt with is in unlist() merging the names together, as you can see in your example given: "V1", "V2" and "V3". Because off interpreting the names later as identifiers in db queries I'm really interested in getting something like list("a"=c("1"=1), "b"=c("1"=2, "2"=5), "c"=c("1"=3), "d"=c("1"=4), "e"=c("1"=6)) for the above input. 
> By giving the result this way I'm able to extract both names from two sets as well as the according value between both items.
> 
> One point could be to build a matrix but this matrix would have many NA's. So I prefer Lists of Lists.
> 
> Any ideas?
> 
> cheers
> 	Jan
> 
> -----UrsprÃ¼ngliche Nachricht-----
> Von: Liaw, Andy [mailto:andy_liaw at merck.com] 
> Gesendet: Montag, 15. August 2005 17:31
> An: Jan Hummel; r-help at stat.math.ethz.ch
> Betreff: RE: [R] Re-sort list of vectors
> 
> If all vectors in the list have the same length, why not use a matrix?  Then you'd just transpose the matrix if you need to.  If you really have to have it as a list, here's one possibility:
> 
> > x <- list("1"=c(a=1, b=2, c=3), "2"=c(a=4, b=5, c=6)) x
> $"1"
> a b c
> 1 2 3 
> 
> $"2"
> a b c
> 4 5 6 
> > as.list(as.data.frame(t(matrix(unlist(x), nrow=3))))
> $V1
> [1] 1 4
> 
> $V2
> [1] 2 5
> 
> $V3
> [1] 3 6
> 
> Andy
> 
> 
> > From: Jan Hummel
> > 
> > Hi.
> > Can anyone suggest a simple way to re-sort in R a list of vectors of 
> > the following form?
> > 
> > input
> > $"1"
> > 	a	b	c
> > 	1	2	3
> > $"2"
> > 	a	b	c
> > 	4	5	6
> > 
> > Output should be something like:
> > "a"
> > 	"1" 1
> > 	"2" 4
> > "b"
> > 	"1" 2
> > 	"2" 5
> > "c"
> > 	"1" 3
> > 	"2" 6
> > 
> > I've been futzing with mapply(), outer(), split(), rbind() and so on 
> > but haven't found an elegant solution.
> > 
> > Thanks,
> > Jan.
> > 
> > P.S. E-mailed CCs of posted replies appreciated.
> > 
> > ______________________________________________
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> > 
> > 
> >
> 
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