[R] a question about swap space, memory and read.table()

[Liaw, Andy]

> From: Hu Chen
> 
> Hi all 
> Two computers:
> one is my desktop PC, windows2000, R 1.9.1. Physical RAM 256MB, Swap
> (Virtual memory)  384Mb. When I allocate a large matrix, it firstly
> uses up RAM, then use swap space. In windows' task manager, the usage
> of memory could exceed my physic RAM's size.
> The other machine is a remote server. Windows XP, R 1.9.1 
> Physical RAM 2GB.
> Swap space 4GB. I use "R --max-mem-size=4000M" to start R. However
> when I allocate a large matrix or data frame, it uses up all RAM then
> exits with a error message" cannot allocate vector of size 7812 Kb ".
> The Swap space is not used at all !

Please do read
http://cran.r-project.org/bin/windows/base/rw-FAQ.html#There-seems-to-be-a-l
imit-on-the-memory-it-uses_0021.

> What's more, I found that the read.table() function is really 
> a waste of memory.
> > ft <- read.table("filepath")
> > object.size(ft)
> object.size(ft)
> [1] 192000692
> only 192Mb.
> however, in the windows task manager it shows that this process takes
> nearly 800Mb memory.
> I used gc() to collect garbarge. Howerver it doesn't help.
> Any guys have methods to release the wasted memory?

This has been asked and answered on R-help many times (good candidate to add
to the FAQ?).  As an example, see:
http://tolstoy.newcastle.edu.au/R/help/04/06/1662.html

Andy



> thank you all.
> Regards
> 
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