You did not show the code you used to populate your
object, but consider the following ways to make as.list(1:50000)
via repeated assignments:
> system.time( { z0 <- list() ; for(i in 1:50000)z0[i] <- list(i) } )
user system elapsed
13.34 0.00 13.42
> system.time( { z1 <- list() ; for(i in 1:50000)z1[[i]] <- i } )
user system elapsed
12.98 0.00 13.36
> system.time( { z2 <- vector("list",50000) ; for(i in 1:50000)z2[i] <-
> list(i) } )
user system elapsed
0.28 0.00 0.26
> system.time( { z3 <- vector("list",50000) ; for(i in 1:50000)z3[[i]] <- i } )
user system elapsed
0.22 0.00 0.20
> identical(z0,z1) && identical(z0,z2) && identical(z0,z3)
[1] TRUE
Preallocating a vector to its ultimate size can be much faster than
repeatedly expanding it.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf Of André Rossi
> Sent: Wednesday, September 07, 2011 3:08 PM
> To: r-help@r-project.org
> Subject: [R] Very slow assignments
>
> I'm creating an object of a S4 class that has two slots: ListExamples, which
> is a list, and idx, which is an integer (as the code below).
>
> Then, I read a data.frame file with 10000 (ten thousands) of lines and 10
> columns, do some pre-processing and, basically, I store each line as an
> element of a list in the slot ListExamples of the S4 object. However, any
> kind of assignment operation (<-) that I try to do after this took a
> considerable time.
>
> Can anyone explain me why dois it happen? Is it possible to speed up an
> script that deals with a big number of data (it might be data.frame or
> list)?
>
> Thank you,
>
> André Rossi
>
> setClass("Buffer",
> representation=representation(
> Listexamples = "list",
> idx = "integer"
> )
> )
>
> [[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
