Re: [R] renaming objects

From: Benilton Carvalho <bcarvalh_at_jhsph.edu>
Date: Mon, 03 Mar 2008 18:11:27 -0500

or, in other terms:

 > set.seed(1)
 > x <- runif(1e7)
 > x.add <- tracemem(x)
 > y <- x
 > y.add <- tracemem(y)
 > identical(x.add, y.add)

[1] TRUE ie, both objects have the same memory address - therefore, not a copy:

 > x.add
[1] "<0x2000000>"
 > y.add
[1] "<0x2000000>"

now, observe what happens when you modify "y"

 > y[1] <- 1
tracemem[0x2000000 -> 0x6c4c000]:
 > tracemem(y)
[1] "<0x6c4c000>"

now, it's a copy... =)

b

On Mar 3, 2008, at 5:48 PM, hadley wickham wrote:

> On Mon, Mar 3, 2008 at 4:37 PM, Rolf Turner
> <r.turner_at_auckland.ac.nz> wrote:

>>
>> On 4/03/2008, at 10:38 AM, Ericka Lundström wrote:
>>
>>> On 03/03/2008, at 22.20, Giles.Crane_at_doh.state.nj.us 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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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. Received on Mon 03 Mar 2008 - 23:37:07 GMT

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