R help - Aug 2011 - a question on list manipulation

Hi R users,

I have a list:
> x
$A
[1] "a"  "b"  "c"
$B
[1] "b"  "c"
$C
[1] "c"

I want to convert it to a lowercase-to-uppercase list like
this:
> y
$a
[1] "A"
$b
[1] "A"  "B"
$c
[1] "A"  "B"  "C"

In a word, I want to reverse the list names and the elements under
each list name. Is there any quick way to do that? Thanks
-- 
Best,
Zhenjiang

There are a few moving pieces to do this:

1) the toupper and tolower functions. These can do almost everything you
need:

x = lapply(x,toupper) ## This changes the things inside x but won't change
the names

2) Now, there are two ways to think about getting the elements from one list
to another: I'd prefer think about changing the list names and order while
leaving the elements in the lists (as for big data it will be more memory
efficient) but you could work on actually moving things.

Here it's easy:

first reverse

x = rev(x)

now you have the problem that "c" is the first element of the list so
you
just need to reverse the whole list and you might as well make them
lowercase while you are at it

names(x) = tolower(names(x)[3:1]) # 3:1 will reorder the list, use length(x)
more generally

Altogether,
x = rev(lapply(x,toupper))
names(x) = tolower(names(x)[3:1])
gives us
>x
$a
[1] "C"

$b
[1] "B" "C"

$c
[1] "A" "B" "C"

as desired.

By the way, this is a very odd request: are you sure this is really what you
need to do? If you describe the more general framework, we can probably help
with some more efficient data management.

Hope this helps,

Michael Weylandt

On Fri, Aug 5, 2011 at 12:05 PM, zhenjiang xu
<zhenjiang.xu@gmail.com>wrote:
> Hi R users,
>
> I have a list:
> > x
> $A
> [1] "a"  "b"  "c"
> $B
> [1] "b"  "c"
> $C
> [1] "c"
>
> I want to convert it to a lowercase-to-uppercase list like this:
> > y
> $a
> [1] "A"
> $b
> [1] "A"  "B"
> $c
> [1] "A"  "B"  "C"
>
> In a word, I want to reverse the list names and the elements under
> each list name. Is there any quick way to do that? Thanks
> --
> Best,
> Zhenjiang
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

On Aug 5, 2011, at 12:05 PM, zhenjiang xu wrote:
> Hi R users,
>
> I have a list:
>> x
> $A
> [1] "a"  "b"  "c"
> $B
> [1] "b"  "c"
> $C
> [1] "c"
>
> I want to convert it to a lowercase-to-uppercase list like this:
>> y
> $a
> [1] "A"
> $b
> [1] "A"  "B"
> $c
> [1] "A"  "B"  "C"
>
> In a word, I want to reverse the list names and the elements under
> each list name. Is there any quick way to do that? Thanks
The obvious way would be:

names(lll) <- to.upper(names(lll)
lll <- lapply(lll, to.lower)


(If you had offered code that would construct the list, I would have  
tested it.)
-- 

David Winsemius, MD
West Hartford, CT

toupper()/tolower()

are the functions to convert the letters.

lapply()

can be used to apply this to different list elements and

names()

is helpfull to convert the names of your list.



HTH
Jannis

On 08/05/2011 06:05 PM, zhenjiang xu wrote:
> Hi R users,
>
> I have a list:
>> x
> $A
> [1] "a"  "b"  "c"
> $B
> [1] "b"  "c"
> $C
> [1] "c"
>
> I want to convert it to a lowercase-to-uppercase list like this:
>> y
> $a
> [1] "A"
> $b
> [1] "A"  "B"
> $c
> [1] "A"  "B"  "C"
>
> In a word, I want to reverse the list names and the elements under
> each list name. Is there any quick way to do that? Thanks

On 05/08/2011 12:05 PM, zhenjiang xu wrote:
> Hi R users,
>
> I have a list:
> >  x
> $A
> [1] "a"  "b"  "c"
> $B
> [1] "b"  "c"
> $C
> [1] "c"
>
> I want to convert it to a lowercase-to-uppercase list like this:
> >  y
> $a
> [1] "A"
> $b
> [1] "A"  "B"
> $c
> [1] "A"  "B"  "C"
>
> In a word, I want to reverse the list names and the elements under
> each list name. Is there any quick way to do that? Thanks
I interpreted this question differently from the others, and your 
example is ambiguous as to which is the right interpretation.  I thought 
you wanted to swap names and elements,  so

 > x <- list(A=c("d", "e", "f"),
B=c("d", "e"), C=c("d"))
 > x
$A
[1] "d" "e" "f"

$B
[1] "d" "e"

$C
[1] "d"

would become

 > list(d=c("A", "B", "C"), e=c("A",
"B"), f="A")
$d
[1] "A" "B" "C"

$e
[1] "A" "B"

$f
[1] "A"

I don't know a slick way to do this; I'd just do it by brute force, 
looping over the names of x.

Duncan Murdoch