[R] Environments

[Bill.Venables at csiro.au]

What you are trying to do is make R behave like a macro language, which is not a good idea at all.  Better to use R as it was designed to be used rather than make it behave like something it wasn't.

It also follows that trying to do this is going to be tricky.  Here is one way:

RENAME <- function(table, from, to) {
  X <- deparse(substitute(table))
  k <- which(names(table) == from)
  names(table)[k] <- to
  assign(X, table, pos = parent.frame())
  invisible(table)
}

### at test

> x <- structure(1:4, names = c("A","B","C","D"))
> x
A B C D 
1 2 3 4 
> RENAME(x, "C", "Z")
> x
A B Z D 
1 2 3 4 
> 

-- but don't do it, there's a sport!

Your solution would work if you were just able to use it in an assignment

x <- rename(x, "C", "Z")

but your function could do with a little tidying up.


Bill Venables.
________________________________________
From: r-help-bounces at r-project.org [r-help-bounces at r-project.org] On Behalf Of Philip Whittall [Philip.whittall at detica.com]
Sent: 02 April 2009 19:31
To: r-help at r-project.org
Subject: [R] Environments

Dear List,

No doubt I am going around this the wrong way, and hopefully one of you
will be able to tell me how to go about it the right way.
I want to change the names of an object inside a function and have it
stay changed in the global environment. I can only
effect the change inside the function as follows ...

> x<-1:4;names(x)<-c("A","B","C","D")
> x
A B C D
1 2 3 4
> rename<-function(table, from,
to){names<-names(table);position<-sum((names==from)*1:length(names));nam
es(table)[position]<-to;table}
> rename(x,"C","Z")
A B Z D
1 2 3 4
> x
A B C D
1 2 3 4
>

I am running R version 2.8.0 on a windows XP platform,

Thanks in anticipation,

Philip



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