Array R-documentation states
The values in the data vector give the values in the array in the same order as in FORTRAN, that is, the "main order of the column" , with the first index working fastest and the last index slower .
He then gives an explanatory example of this, loading the data into a two-dimensional array:
> x <- array(1:20, dim=c(4,5)) # Generate a 4 by 5 array.
> x
[,1] [,2] [,3] [,4] [,5]
[1,] 1 5 9 13 17
[2,] 2 6 10 14 18
[3,] 3 7 11 15 19
[4,] 4 8 12 16 20
From experience with other languages, I would have thought that x[1, 2], instead x[2, 1], will be 2, but it's pretty easy to adjust my thinking. However, as fast as I complete my mental shift of the model, the following example breaks it into pieces:
> i <- array(c(1:3,3:1), dim=c(3,2))
> i # i is a 3 by 2 index array.
[,1] [,2]
[1,] 1 3
[2,] 2 2
[3,] 3 1
> x[i] # Extract those elements
[1] 9 6 3
, , , x[1, 3], x[2,2] x[3, 1]. , " "?
, , i 2 3, R x[i] x[i[1, 1], i[2, 1]], x[i[1, 2], i[2, 2]], .... , R x[i[1, 1], i[1, 2]], x[i[2, 1], i[2, 2]], ...
R ?