Hi,
Another way would be:
library(arrayhelpers)
slice(aperm(x1,c(2,1)),j=1)
#[1] 0.6439062 0.7139397 0.6017418
slice(aperm(x2,c(2,1,3)),j=1)
# [,1] [,2]
#[1,] 0.026671344 0.2116831
#[2,] 0.003903368 0.1551140
slice(aperm(z,c(2,1,3)),j=1)
# [,1] [,2] [,3] [,4]
#[1,] 1 7 13 19
#[2,] 3 9 15 21
#[3,] 5 11 17 23
#or
array(z[slice.index(z,1)==1],dim= dim(z)[2:3])
# [,1] [,2] [,3] [,4]
#[1,] 1 7 13 19
#[2,] 3 9 15 21
#[3,] 5 11 17 23
array(x2[slice.index(x2,1)==1],dim= dim(x2)[2:3])
# [,1] [,2]
#[1,] 0.026671344 0.2116831
#[2,] 0.003903368 0.1551140
array(x1[slice.index(x1,1)==1],dim= dim(x1)[1])
#[1] 0.6439062 0.7139397 0.6017418
A.K.
----- Original Message -----
From: arun <smartpink...@yahoo.com>
To: Martin Ivanov <tra...@abv.bg>
Cc: R help <r-help@r-project.org>; Berend Hasselman <b...@xs4all.nl>; Bert
Gunter <gunter.ber...@gene.com>
Sent: Sunday, May 26, 2013 11:48 AM
Subject: Re: [R] avoiding eval parse with indexing
Hi,
You could use:
library(abind)
#using Berend's and Bert's example
x1 <- array(runif(9),dim=c(3,3))
x2 <- array(runif(8),dim=c(2,2,2))
z <- array(1:24,dim=2:4)
#applying your code:
eval(parse(text=paste0("x1[1",paste(rep(",",length(dim(x1))-1),collapse=""),"]")))
#[1] 0.6439062 0.7139397 0.6017418
eval(parse(text=paste0("x2[1",paste(rep(",",length(dim(x2))-1),collapse=""),"]")))
# [,1] [,2]
#[1,] 0.026671344 0.2116831
#[2,] 0.003903368 0.1551140
eval(parse(text=paste0("z[1",paste(rep(",",length(dim(z))-1),collapse=""),"]")))
# [,1] [,2] [,3] [,4]
#[1,] 1 7 13 19
#[2,] 3 9 15 21
#[3,] 5 11 17 23
asub(x1,1,1,drop=TRUE)
#[1] 0.6439062 0.7139397 0.6017418
asub(x2,1,1,drop=TRUE)
# [,1] [,2]
#[1,] 0.026671344 0.2116831
#[2,] 0.003903368 0.1551140
asub(z,1,1,drop=TRUE)
# [,1] [,2] [,3] [,4]
#[1,] 1 7 13 19
#[2,] 3 9 15 21
#[3,] 5 11 17 23
A.K.
----- Original Message -----
From: Martin Ivanov <tra...@abv.bg>
To: r-help@r-project.org
Cc:
Sent: Sunday, May 26, 2013 9:56 AM
Subject: [R] avoiding eval parse with indexing
Hello,
I would like to get an advice on how the notorious eval(parse()) construct
could possibly
be avoided in the following example. I have an array x, which can have
different number of dimensions,
but I am only interested in extracting, say, the first element of the first
dimension. Currently I achieve this
in this way:
eval(parse(text=paste0("x[1", paste(rep(", ", length(dim(x)) - 1),
collapse=""), "]")))
Is it possible to avoid the eval parse here? How?
Best regards,
Martin
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