[R] multidimensional list

[Jonathan Rougier]

Hi Sven,

On Wed, 23 May 2001, Sven Garbade wrote:

> is it possible to create a multidemensional list? Haven't found anything
> in the list() help page. 

Yes it is, although there are some slight bugs to be aware of.  If you
have

> fred <- as.list(1:12)

then you can make fred into a dimensioned list simply by doing 

> dim(fred) <- c(3, 4)

and then you can do things like

> fred[[1, 2]] <- list(happy = 1:10, sad = "armadillo")

There are a couple of things that don't work very well.  At version 1.2.1
(a bit out of date but my latest version) you will get a segmentation
fault if you do the incorrect

> fred[[1, ]]

but this has been corrected on later versions.  It is still a bit
difficult to make a dimensioned list by doing

> array(list(happy = 1:10, sad = "armadillo"), c(3, 4))

but that is because rep does not (yet) handle lists *except* simple lists
like

> array(list(happy = 1:10), c(3, 4))

I believe that this is being addressed.  But with ingenuity you can get
around this, for example I have used a construction like

> fred <- array(list(list(happy = 1:10, sad = "armadillo")), c(3, 4))

Cheers, Jonathan.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE
tel: +44 (0)191 374 2361, fax: +44 (0)191 374 7388
http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html

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