accessing the attributes of a list inside lapply()

Hello R-users, 

I have the following problem, that I want to solve efficiently:

I have a named list, for example:
l <- list(a = 1, b = 3, c = 'asd')
l
$a
[1] 1

$b
[1] 3

$c
[1] "asd"

I know that I can iterate through it using lapply() function, but I
would also like to able to get the list names or some attributes of l
in the lapply(). For example if I use names() function in the call of
lapply() I get:
lapply(l, names)
$a
NULL

$b
NULL

$c
NULL

My question is if I can get something like:
lapply(l, get_attr)
$a
[1] a

$b
[1] b

$c
[1] c

I can do this very easy with a for() loop but my list is quite big and
I would like to get a decent running time. I don't need only the
attributes of the list(I can obtain them by using attributes() or
attr() function), but for my list the names of the elements are given
me information that I need. Also I must mention that the elements of
the list can by of any type.

Any solution is welcome.

Many thanks, 

Adrian
Adrian Alexa             
Max-Planck-Institut fuer Informatik  
Stuhlsatzenhausweg 85 Room 514 
66123 Saarbruecken, Germany
Hi,

What about:

 >  as.list(names(l))
[[1]]
[1] "a"

[[2]]
[1] "b"

[[3]]
[1] "c"

HTH,

Eric
Hello R-users,

I have the following problem, that I want to solve efficiently:

I have a named list, for example:

l <- list(a = 1, b = 3, c = 'asd')
l
$a
[1] 1

$b
[1] 3

$c
[1] "asd"

I know that I can iterate through it using lapply() function, but I
would also like to able to get the list names or some attributes of l
in the lapply(). For example if I use names() function in the call of
lapply() I get:

lapply(l, names)
$a
NULL

$b
NULL

$c
NULL

My question is if I can get something like:

lapply(l, get_attr)
$a
[1] a

$b
[1] b

$c
[1] c

I can do this very easy with a for() loop but my list is quite big and
I would like to get a decent running time. I don't need only the
attributes of the list(I can obtain them by using attributes() or
attr() function), but for my list the names of the elements are given
me information that I need. Also I must mention that the elements of
the list can by of any type.

Any solution is welcome.

Many thanks,

Adrian

--
Adrian Alexa
Max-Planck-Institut fuer Informatik
Stuhlsatzenhausweg 85 Room 514
66123 Saarbruecken, Germany

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Maybe I misunderstand your problem, but I wonder if you've 
considered "names": 

 > l <- list(a = 1, b = 3, c = 'asd')
 > names(l)
[1] "a" "b" "c"    

      hope this helps.  spencer graves
p.s.  I can't parse your "lapply(l, get_attr)".  In R 1.9.1 and R 2.0.0 
Patched, I get the following: 

 > lapply(l, get_attr)
Error in match.fun(FUN) : Object "get_attr" not found

Hello R-users, 

I have the following problem, that I want to solve efficiently:

I have a named list, for example:

l <- list(a = 1, b = 3, c = 'asd')
l

$a
[1] 1

$b
[1] 3

$c
[1] "asd"

I know that I can iterate through it using lapply() function, but I
would also like to able to get the list names or some attributes of l
in the lapply(). For example if I use names() function in the call of
lapply() I get:

lapply(l, names)

$a
NULL

$b
NULL

$c
NULL

My question is if I can get something like:

lapply(l, get_attr)

$a
[1] a

$b
[1] b

$c
[1] c

I can do this very easy with a for() loop but my list is quite big and
I would like to get a decent running time. I don't need only the
attributes of the list(I can obtain them by using attributes() or
attr() function), but for my list the names of the elements are given
me information that I need. Also I must mention that the elements of
the list can by of any type.

Any solution is welcome.

Many thanks, 

Adrian 

Spencer Graves, PhD, Senior Development Engineer
O:  (408)938-4420;  mobile:  (408)655-4567