[R] renaming objects

[Benilton Carvalho]

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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