[R] renaming objects

[Rolf Turner]

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.

	That being said, I'm pretty sure that the answer to the original
	question ``Is there a way ... ?'' is ``No.''  The R-Core people
	will be able to provide a definitive answer, but it appears to me
	that the way a name is associated with an object is buried deep
	in the innards of R and is not accessible to the user.

	At this stage, I'd like to enquire ***why*** is it desired to
	be able to do this?  The one rationale that I can think of is the
	situation that x is so huge that it is impossible to make a copy
	of it (via ``y <- x'') without exceeding R's memory capacity.

	If x is not that huge, one can simply do ``y <- x'' and then
	``rm(x)'' and presto one has changed the object's name from ``x''
	to ``y''.

	I have written my own little utility function ``mv()'', imitating
	the Unix command ``mv'' to facilitate this:

	mv <- function (a, b) {
     		anm <- deparse(substitute(a))
     		bnm <- deparse(substitute(b))
     		if (!exists(anm,where=1,inherits=FALSE))
         		stop(paste(anm, "does not exist.\n"))
     		if (exists(bnm,where=1,inherits=FALSE)) {
         		ans <- readline(paste("Overwrite ", bnm, "? (y/n) ", sep =  
""))
         	if (ans != "y")
             	return(invisible())
     	}
     	assign(bnm, a, pos = 1)
     	rm(list = anm, pos = 1)
     	invisible()
	}

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