Message-ID: <CAAmySGOKZtbBShbBX+viu9f49rFJn==R26bM1OwpBQqbrR-xxQ@mail.gmail.com>
Date: 2011-10-06T13:12:33Z
From: R. Michael Weylandt
Subject: Running *slow*
In-Reply-To: <67029D1C-F089-4B5E-9ACD-B9362989116A@gmail.com>
?unique
x <- matrix(c(1:6, 6:1),ncol=2)
x.temp <- x
dim(x.temp) <- NULL
unique(x.temp)
Michael
On Thu, Oct 6, 2011 at 8:37 AM, Thomas <chesney.alt at gmail.com> wrote:
> Anyone got any hints on how to make this code more efficient? An early
> version (which to be fair did more than this one is) ran for 330 hours and
> produced no output.
>
> I have a two column table, Dat, with 12,000,000 rows and I want to produce a
> lookup table, ltable, in a 1 dimensional matrix with one copy of each of the
> values in Dat:
>
> for (i in 1:nrow(Dat))
> {
> for (j in 1:2)
> {
> #If next value is already in ltable, do nothing
> if (is.na(match(Dat[i,j], ltable))){ltable <- rbind(ltable,Dat[i,j])}
> }
> }
>
> but it takes forever to produce anything.
>
> Any advice gratefully received.
>
> Thomas
>
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