[R] Extracting list names within a looped function

[Berend Hasselman]

On 15-11-2012, at 11:14, Gaj Stan (BIGCAT) wrote:

> Hello all,
> 
> I have the following problem:
> 
> 1) A list was defined as 'a'
> 
> a <- list("var1"=c(100:1), "var2"=c(1:100), "var3"=rnorm(100))
> 
> 2) a function 'foo' was defined that extracts the variable name assigned to x using the deparse(substitute()) functionality. This name will then be used within the function to generate specific output files, etc.
> 
> foo <- function(x) {
>  print( deparse(substitute(x)) )
> }
> 
> However, I am currently interested in looping through all list variables and extract the list variable name from within the function. The current loop (see below) will result in
> 
> for(i in 1:length(a)) {
>  foo(a[[i]])
> }
> [1] "a[[i]]"
> 
> which actually does what I expected of deparse(substitute(x)), but is not what I wanted. I would like to end up with something like
> 
> [1] "var1"
> [1] "var2"
> [1] "var3"
> 
> or
> 
> [1] "a[[\"var1\"]]"
> [1] "a[[\"var2\"]]"
> [1] "a[[\"var3\"]]"
> 
> Keep in mind that x has to be a matrix, and not a list. This to keep the function as general as possible.
> 
> Does anyone have any idea on how to tackle this? Is deparse(substitute(x)) here the best way to go? Are there alternatives?

I'm not sure if I understand what you want but will this give you what you seem to want:

names(a)

Berend