[R] vectorizing problem

[Dimitris Rizopoulos]

try this:

GPL <- data.frame(x = c(2315100, 2315106),
     y = c("NR_024005,NR_024004,AK093685", "DQ786314"))

sp <- strsplit(as.character(GPL$y), ",")
ni <- sapply(sp, length)
data.frame(x = rep(GPL$x, ni), y = unlist(sp))


I hope it helps.

Best,
Dimitris


On 10/4/2010 7:54 PM, Dylan Miracle wrote:
> Hello,
>
> I have a two column dataframe that
> has entries that look like this:
>
> 2315100       NR_024005,NR_024004,AK093685
> 2315106       DQ786314
>
> and I want to change this to look like this:
>
> 2315100       NR_024005
> 2315100       NR_024004
> 2315100       AK093685
> 2315106       DQ786314
>
> I can do this with the following "for" loop but the dataframe (GPL)
> has ~140,000 rows and this takes about 15 minutes:
>
>
> extGPL<- matrix(nrow=0,ncol=2)
> for (i in 1:length(GPL[,2])){
>         aa<- unlist(strsplit(as.character(GPL[i,2]),"\\,"))
>         bb<- rep(as.numeric(as.character(GPL[i,1])), length(aa))
>         cc<- matrix(c(bb,aa),ncol = 2)
>         extGPL<- rbind(extGPL,cc)
> }
>
> Is there a way to vectorize this?
>
> Thanks,
>
> Dylan Miracle
> University of Minnesota
> GCD Department
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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