[R] Query: list within a list

[R. Michael Weylandt]

It's certainly possible and I don't think you get any grueling
inefficiencies. along the way.

Another way that might or might not make sense for you is to use a
nifty trick I saw Gabor and Duncan M use a few weeks ago: you can give
dimensionality to a list and then subset it in the "normal" ways:
e.g.,

x <- list(a = 1, b = 2, c = 3, d = 4)
dim(x) <- c(2,2)
colnames(x) <- c("a", "b")

x[2,]
x[,2]

x[[2]]]

x[,"a"]

Might be of help for some nifty indexing. (Or it might look so crazy
to scare folks away: your call)

Michael
On Wed, Feb 22, 2012 at 10:17 AM, Stefano Sofia
<stefano.sofia at regione.marche.it> wrote:
> Dear R users,
> I have difficulty to create a list within a list.
> Example: with
>
>> A <- vector(mode="list", 4)
>
> I create a list of 4 elements:
>> A
> [[1]]
> NULL
>
> [[2]]
> NULL
>
> [[3]]
> NULL
>
> [[4]]
> NULL
>
> In each element of this list I can store, for example, a matrix:
> A[[1]] <- matrix ...
>
> I need each element of A to be a list (all the lists of the same length), and then store matrices within these lists.
> Have I explained it in a reasonable way?
> Is it possible?
> If yes, is it efficient? For my purposes, I need to have A a list of length 20000 or 30000 (even 50000 possibily), and the lists within A of length 1000 and store square matrices of dimension 13.
>
> Thank you for your attention and your help
> Stefano Sofia PhD
>
>
>
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