[R] Naming elements of a list

[Greg Snow]

It may be easier for us to help you if you tell us what you are actually
trying to accomplish (naming the elements of the list is easy, but doing
that won't fix your problems).

Note that when you attach a list it attaches a copy of the list, any
changes to the original list will not be seen in the attached copy.
Also, changing the value of 'i' after using it in the list will not
affect the value in the list. 

You should really read up on lexical scoping, that may be the solution
to your question, try rewriting your functions as:

free_driver <- function(){
  i <- 25

  free_test <- function(){
   cat("i=",i,"\n\n")
  }

  free_test()
}

To see if that is accomplishing what you want to do,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at intermountainmail.org
(801) 408-8111
 
 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Thomas L Jones, PhD
> Sent: Thursday, November 22, 2007 1:16 AM
> To: R-project help
> Subject: [R] Naming elements of a list
> 
> I have a numeric vector of lenth 1. I am trying to use it 
> inside a function just by giving its name, rather than 
> specifying it as an argument to the function. I am aware that 
> there is an attach function which you need to call. The 
> attach function will accept a list. However, I don't seem to 
> be able to create the list properly. (Or should I use a frame 
> instead?)
> 
> free_driver <- function (){
> i <- numeric (1)
> attach (as.list (i))
> i <- 25
> 
> free_test ()
> 
> }
> free_test <- function (){
> print ("i =")
> print (i)
> return ()
> 
> }
> 
> Anyway, here is the output, starting with the load operation:
> 
> ------------------------------------------------------------------
> 
> > free_driver <- function (){
> + i <- numeric (1)
> + attach (as.list (i))
> + i <- 25
> +
> + free_test ()
> +
> + }
> > free_test <- function (){
> + print ("i =")
> + print (i)
> + return ()
> +
> + }
> > free_driver ()
> Error in attach(as.list(i)) : all elements of a list must be named
> >
> --------------------------------------------------------------
> 
> Is there an easy way to name all elements of a list?
> 
> Your advice?
> 
> Tom Jones
> 
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