R help - Jan 2010 - changing a list element's name during execution in lapply - possible?

Happy New Year, all!

I want to do calculations on each element of a list l, but i want the  
returned list element to be named differently after the calculation.
Is it possible to do the renaming somehow within the lapply call?

	l <- list(a=NA, b=NA)
	lapply(l, function(x) {names(x) <- "new name";  return(x) })

This does not work, any ideas?
TIA

???????????????????????????????????????
Mark Heckmann
Dipl. Wirt.-Ing. cand. Psych.
Vorstra?e 93 B01
28359 Bremen
Blog: www.markheckmann.de
R-Blog: http://ryouready.wordpress.com

On Jan 1, 2010, at 8:21 AM, Mark Heckmann wrote:
> Happy New Year, all!
>
> I want to do calculations on each element of a list l, but i want  
> the returned list element to be named differently after the  
> calculation.
> Is it possible to do the renaming somehow within the lapply call?
>
> 	l <- list(a=NA, b=NA)
> 	lapply(l, function(x) {names(x) <- "new name";  return(x) })
>
> This does not work, any ideas?
It did "work" in the sense that it created a list of the same  
structure with each node now named "new name". If you want that named
list to become "l", then you need to do an assignment:

l <- lapply(l, function(x) {names(x) <- "new name";  return(x)
})
 > l
$a
new name
       NA

$b
new name
       NA



-- 
David.
> TIA
>
> ???????????????????????????????????????
> Mark Heckmann
> Dipl. Wirt.-Ing. cand. Psych.
> Vorstra?e 93 B01

Try this:

# same args as lapply.  FUN must return named components.
lapplyWithRename <- function(...) {
	x <- lapply(...)
	names(x) <- sapply(x, names)
	lapply(x, function(x) { names(x) <- NULL; x })
}

# test function - if x is "A" then f returns c("Name A" =
"A")
f <- function(x) structure(x, .Names = paste("Name", x))

L <- list(a="A", b="B")
lapplyWithRename(L, f)

Output looks like this:
> lapplyWithRename(L, f)
$`Name A`
[1] "A"

$`Name B`
[1] "B"


On Fri, Jan 1, 2010 at 8:21 AM, Mark Heckmann <mark.heckmann at gmx.de>
wrote:
> Happy New Year, all!
>
> I want to do calculations on each element of a list l, but i want the
> returned list element to be named differently after the calculation.
> Is it possible to do the renaming somehow within the lapply call?
>
> ? ? ? ?l <- list(a=NA, b=NA)
> ? ? ? ?lapply(l, function(x) {names(x) <- "new name";
?return(x) })
>
> This does not work, any ideas?
> TIA
>
> ???????????????????????????????????????
> Mark Heckmann
> Dipl. Wirt.-Ing. cand. Psych.
> Vorstra?e 93 B01
> 28359 Bremen
> Blog: www.markheckmann.de
> R-Blog: http://ryouready.wordpress.com
>
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