[R] vectorizing problem

[Gabor Grothendieck]

On Mon, Oct 4, 2010 at 1:54 PM, Dylan Miracle <dylan.miracle at gmail.com> 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:

Try this assuming that the columns of GPL are character.  You may need
to use as.character first if they are factor:

library(reshape2)
V2 <- strsplit(GPL$V2, ",")
names(V2) <- GPL$V1
melt(V2)

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