Robert Gentleman wrote:
> On Tue, Oct 16, 2001 at 04:40:34PM +0100, Rita Ribeiro wrote:
> > Hi,
> >
> > In order to avoid deep copies by passing large arguments to
functions or> >
> > returning values, I'm trying to do the assignment of variables in
a
> > given environment. The problem is when I try to assign a structure:
a> > list for example.
> >
> > If I have:
> > ind <- c("a","b")
> >
> > my idea is doing something like
> >
> > l <- alist()
> > l[ind] <- as.list(c(20,40))
> >
> > in a given environment.
> >
> >
> >
> > Example:
> > ref <- new.env()
> > (.....)
> > assign("l",alist(),env=ref)
> >
> >
> > If I do
> > assign("l$a",20,env=ref)
> >
> > it creates me a new variable in the ref environment named
"l$a"
> >
> This is what you asked it to do.
> Environments work at the level of whole objects. I'm not sure what
> it would mean for l$a to exist in ref if l doesn't exist in ref.
> So, you just assign l into the environment and retrieve it from the
> environment, using get.
>
> If you you have only one list then perhaps you do not want to put
> the list in, rather just the elements.
>
> names <- names(l)
> for(i in 1:length(l)) assign(names[i], l[[i]], env=ref)
>
> you then have a and b, for example, in the environment and can
> extract them.
>
> If you have two lists, l1 and l2 and both have a's and b's as
> components then you have to put in the whole list (or adopt a
> naming convention).
>
Hi, again
My problem is concerned with the fact that my list will be a list
of lists
which elements will be sucessively appended and defined.
I want to "build" the whole list into the environment. preserving
its structure
(it will be useful for me to be able to manipulate the list later).
More precisely, I want to do ,in a given environment, something
like:
l <- alist()
l$first <- alist()
l$first[ind] <- as.list(c(20,40)) # where ind is local
vector
containind the elements names
l$second <- 50
So If i do
> l
$first
$first$a
[1] 20
$first$b
[1] 40
$second
[1] 50
and
> l$first$b
[1] 40
I'm searching for some alternative to solution to define
this hierarchy
in the designed environment, without needing to use the 'evalq'
command..... Is
there one?
Thanks again,
Rita
>
> One might ask whether you are sure that you need to do this?
> I work on very large data sets and copying has pretty much never
> been an issue.
>
> >
> >
> > So, I did:
> >
> > eval(l <- alist(), env=ref)
> >
> > but this creates the l list both on the current and on the ref
> > environment.
> >
> >
> > The alternative solution that I found out was:
> >
> > evalq(l<-alist(),env=ref)
> >
> > and then
> >
> > evalq(ind <-c("a","b"), env=ref)
> > evalq(l[ind] <- as.list(c(20,40)), env=ref)
> >
> >
> > I would like to know if there is another possible solution, instead
of> > doing these 'evalqs' along the program code.
> >
> >
> > Thanks,
> >
> > Rita
> >
> >
> >
> >
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>
> --
>
+---------------------------------------------------------------------------+
> | Robert Gentleman phone : (617)
632-5250 |> | Associate Professor fax: (617)
632-2444 |> | Department of Biostatistics office: M1B28
> | Harvard School of Public Health email:
rgentlem at jimmy.dfci.harvard.edu |>
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Subject: Re: [R] Assignment of structures on a given environment
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