[R] Running *slow*

[Gerrit Eichner]

Hi, Thomas,

if I'm not completely mistaken

Dat2 <- match( t( Dat), ltable)

should do what you want.

  Hth -- Gerrit

On Fri, 7 Oct 2011, thomas.chesney wrote:

> Thank you Michael and Patrick for your responses. Michael - your code ran in
> under 5 minutes, which I find stunning, and Patrick I have sent the Inferno
> doc to the copier for printing and reading this weekend.
>
> I now have 8 million values in my lookup table and want to replace each
> value in Dat with the index of that value in the lookup table. In line with
> Chapter 2 in the Inferno doc, I created a list of appropriate size first,
> rather than growing it, but still couldn't figure out how to do it without
> looping in R, so it still runs extremely slowly, even just to process the
> first 1000 values in Dat. My original code (before I tried specifiying the
> size of Dat2) was:
>
> Dat2 <- c()
>
> for (i in 1:nrow(Dat))
> {
> for (j in 1:2)
> {
> Dat2 <- c(Dat2, match(Dat[i,j], ltable))
> }}
>
> write(t(edgelist), "EL.txt", ncolumns=2)
>
> Can anyone suggest a way of doing this without looping in R? Or is the
> bottleneck the c function? I am looking at apply this morning, but Gentleman
> (2009) suggests apply isn't very efficient.
>
> --
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