[R] how to reverse a list

[Weiwei Shi]

I forgot to add my bad solution here:

reverseList <- function(xlist){
  blist <- xlist[!is.na(xlist)]
  x0 <- unlist(blist)
  l0 <- length(blist)
  d0 <- as.data.frame(matrix(0, l0, 3))
  d0[,1] <- names(x0)
  d0[,2] <- x0


  # unique llid
  llid <- unique(d0[,2])
  outlist <- list( )
  for (i in 1:length(llid)) {
    each <- llid[i]
    probes <- d0[d0[,2]==each, 1]
    outlist <-  c(outlist, list(probes))
  }
  names(outlist) <- as.character(llid)
  outlist
}

On 4/11/07, Weiwei Shi <helprhelp at gmail.com> wrote:
> Hi, there:
>
> I am wondering if there is a quick way to "reverse" a list like this:
>
> t0 <- list(a=1, b=1, c=2, d=1)
>
> reverst t0 to t1
>
> > t1
> $`1`
> [1] "a" "b" "d"
>
> $`2`
> [1] "c"
>
>
> thanks.
> --
> Weiwei Shi, Ph.D
> Research Scientist
> GeneGO, Inc.
>
> "Did you always know?"
> "No, I did not. But I believed..."
> ---Matrix III
>


-- 
Weiwei Shi, Ph.D
Research Scientist
GeneGO, Inc.

"Did you always know?"
"No, I did not. But I believed..."
---Matrix III