This is interesting!
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 151051 4.1 350000 9.4 350000 9.4
Vcells 94969 0.8 20380703 155.5 30094956 229.7
> a <- runif(1e07)
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 151046 4.1 350000 9.4 350000 9.4
Vcells 10094946 77.1 20380703 155.5 30094956 229.7
> b <- a
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 151047 4.1 350000 9.4 350000 9.4
Vcells 10094946 77.1 20380703 155.5 30094956 229.7
> b <- a + 0
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 151048 4.1 350000 9.4 350000 9.4
Vcells 20094946 153.4 21479738 163.9 30094956 229.7
>
In the last case, R makes an extra copy of "a", because it "thinks" that it
has been modified ???
Ravi.
----------------------------------------------------------------------------
-------
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
----------------------------------------------------------------------------
--------
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of hadley wickham
Sent: Monday, March 03, 2008 5:48 PM
To: Rolf Turner
Cc: r-help; [EMAIL PROTECTED]
Subject: Re: [R] renaming objects
On Mon, Mar 3, 2008 at 4:37 PM, Rolf Turner <[EMAIL PROTECTED]> wrote:
>
> On 4/03/2008, at 10:38 AM, Ericka Lundström wrote:
>
> > On 03/03/2008, at 22.20, [EMAIL PROTECTED] wrote:
> >> Is there a way to rename R objects?
> >> I am looking for a way to rename objects
> >> without making new objects.
> >>
> >> #For example:
> >> x = c(1:40)
> >> # I wish to use a function to rename x, already created, to y,
> >> perhaps by
> >> obj.rename(x,y)
> >> # or
> >> obj.rename("x","y")
> > y <- x # changes x to y with same values.
>
> That makes a new object --- which is precisely what the enquirer
> wanted ***NOT*** to do.
It doesn't though!
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 133095 3.6 350000 9.4 350000 9.4
Vcells 87049 0.7 786432 6.0 478831 3.7
> a <- runif(1e7)
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 133112 3.6 350000 9.4 350000 9.4
Vcells 10087364 77.0 11458389 87.5 10087374 77.0
> b <- a
> gc()
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 133117 3.6 350000 9.4 350000 9.4
Vcells 10087365 77.0 12111308 92.5 10087476 77.0
R will only create a copy if either of a or b is modified.
Hadley
--
http://had.co.nz/
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
