Try: do.call(abind, c(foo, along = 3))
On Tue, Dec 30, 2008 at 1:15 PM, baptiste auguie <ba...@exeter.ac.uk> wrote: > In fact, when writing my post I tried to do exactly what you did in creating > a 3d array from the list, and I failed miserably! This is (imho) partly > because the syntax is not very clean or straightforward as compared to the > apply and *ply family. A list of matrices with equal dimensions is easily > produced by mapply(... , simplify=F), or lapply, while an array needs to be > created in a more verbose manner (as far as i know, some version of a loop). > > I just remembered the abind package which makes this a bit easier, although > the default is not quite as convenient for this purpose as I'd initially > hoped: > > foo <- list(rbind(c(1,2,3),c(4,5,6)),rbind(c(7,8,9),c(10,11,12))) > foo2 <- unlist(foo) > dim(foo2) <- c(dim(foo[[1]]), length(foo)) > > library(abind) > foo3 <- do.call(function(...) abind(..., along=3), foo) > foo2==foo3 > > Best wishes, > > baptiste > > > On 30 Dec 2008, at 18:53, hadley wickham wrote: > >> On Tue, Dec 30, 2008 at 10:21 AM, baptiste auguie <ba...@exeter.ac.uk> >> wrote: >>> >>> I thought this was a good candidate for the plyr package, but it seems >>> that >>> l*ply functions are meant to operate only on separate list elements: >>> >>> Lists are the simplest type of input to deal with because they are >>> already >>> naturally >>> divided into pieces: the elements of the list. For this reason, the l*ply >>> functions don't >>> need an argument that describes how to break up the data structure. >>> >>> (from: plyr: divide and conquer, Hadley Wickham 2008) >>> >>> Perhaps a new case to consider? >> >> Possibly, but here I would argue that the choice of data structure >> isn't quite right - if the matrices all have the same dimension, then >> they should be stored in an array, not a list: >> >> foo <- list(rbind(c(1,2,3),c(4,5,6)),rbind(c(7,8,9),c(10,11,12))) >> foo2 <- unlist(foo) >> dim(foo2) <- c(dim(foo[[1]]), length(foo)) >> >> Then you can use apply (or aaply) directly on that matrix: >> >> apply(foo2, c(1,2), mean) >> apply(foo2, c(1,2), mean, trim = 0.1) >> >> etc. >> >> Hadley >> >> -- >> http://had.co.nz/ > > _____________________________ > > Baptiste Auguié > > School of Physics > University of Exeter > Stocker Road, > Exeter, Devon, > EX4 4QL, UK > > Phone: +44 1392 264187 > > http://newton.ex.ac.uk/research/emag > > ______________________________________________ > 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. > ______________________________________________ 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.
