[R] transposing/rotating XY in a 3D array
Kushantha Perera
kushanthap at ambaresearch.com
Fri May 15 11:35:25 CEST 2009
Try this:
> x <- array(1:12,c(3,2,2))
> x
, , 1
[,1] [,2]
[1,] 1 4
[2,] 2 5
[3,] 3 6
, , 2
[,1] [,2]
[1,] 7 10
[2,] 8 11
[3,] 9 12
> xt <- aperm(x, c(2,1,3))
> xt
, , 1
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 4 5 6
, , 2
[,1] [,2] [,3]
[1,] 7 8 9
[2,] 10 11 12
Good day!
Kushantha Perera | Amba Research
Ph +94 11 235 6281 | Mob +94 77 222 4373
Bangalore * Colombo * London * New York * San José * Singapore * www.ambaresearch.com
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of andzsin
Sent: Friday, May 15, 2009 12:38 PM
To: r-help at r-project.org
Subject: [R] transposing/rotating XY in a 3D array
Dear list,
We have a number of files containing similarly structured data:
file1:
A B C
1 2 3
4 5 6
file2:
A B C
7 8 9
10 11 12
... etc
My part of R receives all these data as an array: 1,2,3... 12 together
with info about dimensions (row,col,fileN) . (
Converting the data into 3D cannot simply done by:
array(x, c(2,3,2))
because breaks the structure (e.g. 1,3,5 is type mismatch)
array(1:12,c(2,3,2))
, , 1
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
...
Of course following R's indexing order (rowIndex is the fastest)
retains the structures, but X and Y dimensions are transposed. (note, c
(2,3,2) => (3,2,2))
array(1:12, c(3,2,2))
, , 1
[,1] [,2]
[1,] 1 4
[2,] 2 5
[3,] 3 6
Its like converting into Japanese vertical reading.
It is not that I cannot get used to it, but I guess it is less error
prone if I have the same order as in the data files.
Now I am using an ad-hoc function (see below) to transpose back the
rotated YX into a XYZ array, but I'd rather go with built-ins, e.g.
byrow=T, or t() -- and also without duplicating my data.
THanks for the advice in advance.
Gabor
<code>
transposeXYinXYZ<-function(x){
y <- array(NA,c(dim(x)[2],dim(x)[1],dim(x)[3]))
for(i in 1:dim(x)[3]){
y[,,i] <- t(x[,,i])
}
return (y)
}xyz <- array(1:24,c(4,3,2))
yxz <- transpose(x)
xyz
yxz
</code>
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