[R] syntax for a list of components from a list

[Joshua Wiley]

Hi,

On Thu, Jan 20, 2011 at 6:59 AM, Maas James Dr (MED) <J.Maas at uea.ac.uk> wrote:
> I'm attempting to generalise a function that reads individual list components, in this case they are matrices, and converts them into 3 dimensional array.  I can input each matrix individually, but want to do it for about 1,000 of them ...
>
> This works
> array2 <- abind(list1[[1]],list1[[2]],list1[[3]],along=3)
>
> This doesn't
> array2 <- abind(list1[[1:3]],along=3)

This is close, but using the `[[` operator is not quite what you want here.

myl <- rep(list(matrix(1:9, 3)), 9)

length(myl) # look at the length of the list (9)
myl[1:3] # select elements 1:3 of the list

## Contrast this with:

myl[[1:2]] # select the 1st element of the list, then the 2nd element of that
myl[[c(3, 1)]] # 3rd element of list, 1st element of that

## This does what you want I think
require(abind) # load relevant package
abind(myl[1:3], along = 3)


Cheers,

Josh

> This doesn't either
> array2 <- abind((list1[[1]]:(list1[[3]]),along=3)
>
> Any thoughts how I can make this work for larger numbers?
>
> Thanks
>
> J
>
> ===============================
> Dr. Jim Maas
> University of East Anglia
>
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/