[R] Extract rows from a list object

[Dimitris Rizopoulos]

try something like this:

n <- 23
x <- array(1:20, dim = c(n, 6))
huge.list <- rep(list(x), 1000)

out <- lapply(1:4, function (i) {
     t(sapply(huge.list, "[", i = i, j = 1:6))
})

out[[1]]
out[[4]]


I hope it helps.

Best,
Dimitris


On 8/24/2010 11:29 AM, Vladimir Mikryukov wrote:
> Dear list members,
>
> I need to create a table from a huge list object,
> this list consists of matrices of the same size (but with different
> content).
>
> The resulting n tables should contain the same rows from all matrices.
>
> For example:
> n<- 23
> x<- array(1:20, dim=c(n,6))
>
> huge.list<- list()
> for (i in 1:1000) {
>      huge.list[[i]]<- x }
>
>
> # One of 1000 matrices
> huge.list[[1]][1:4, 1:6]
>       [,1] [,2] [,3] [,4] [,5] [,6]
> [1,]    1    4    7   10   13   16
> [2,]    2    5    8   11   14   17
> [3,]    3    6    9   12   15   18
> [4,]    4    7   10   13   16   19
> ...
>
> # The result should be like that:
> # One of n tables (with the row 4 from all 1000 matrices):
>       [,1] [,2] [,3] [,4] [,5] [,6]
> [1,]    4    7   10   13   16   19
> [2,]    4    7   10   13   16   19
> [3,]    4    7   10   13   16   19
> [4,]    4    7   10   13   16   19
> ...
> [999,]    4    7   10   13   16   19
> [1000,]    4    7   10   13   16   19
>
>
> # I tried to convert a list object to an array
> ARR<- array(unlist(huge.list), dim = c(dim(huge.list[[1]]),
> length(huge.list)))
> # then split it and use abind function, but it didn't work
>
> Thanks in advance!
> Vladimir
>
> --
> Vladimir Mikryukov
> PhD student
>   Institute of Plant&  Animal Ecology UD RAS,
> Lab. of Population and Community Ecotoxicology
> [8 Marta 202, 620144, Ekaterinburg, Russia]
> Tel.  +7 343 210 38 58 (ext.290)
> Fax: +7 343 260 82 56, +7 343 260 65 00
>
> 	[[alternative HTML version deleted]]
>
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>

-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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