Generalized row and col

Given an array, returns an array of the same size whose elements are sequentially numbered along the \(i^{\rm th}\) dimension.

Usage

arow(a, i)

Arguments

a

array to be converted

i

Number of the dimension

Value

An integer matrix with the same dimensions as a, with element \(\left(n_1,n_2,\ldots n_d\right)\) being \(n_i\).

Author

Robin K. S. Hankin

Note

This function is equivalent to, but faster than, function(a,i){do.index(a,function(x){x[i]})}. However, it is much more complicated.

The function is nominally the same as slice.index() but I have not checked all the edge cases.

Examples

a <- array(0,c(3,3,2,2))
arow(a,2)
#> , , 1, 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    2    3
#> [2,]    1    2    3
#> [3,]    1    2    3
#> 
#> , , 2, 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    2    3
#> [2,]    1    2    3
#> [3,]    1    2    3
#> 
#> , , 1, 2
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    2    3
#> [2,]    1    2    3
#> [3,]    1    2    3
#> 
#> , , 2, 2
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    2    3
#> [2,]    1    2    3
#> [3,]    1    2    3
#> 
(arow(a,1)+arow(a,2)+arow(a,3)+arow(a,4))%%2
#> , , 1, 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    0    1    0
#> [2,]    1    0    1
#> [3,]    0    1    0
#> 
#> , , 2, 1
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    0    1
#> [2,]    0    1    0
#> [3,]    1    0    1
#> 
#> , , 1, 2
#> 
#>      [,1] [,2] [,3]
#> [1,]    1    0    1
#> [2,]    0    1    0
#> [3,]    1    0    1
#> 
#> , , 2, 2
#> 
#>      [,1] [,2] [,3]
#> [1,]    0    1    0
#> [2,]    1    0    1
#> [3,]    0    1    0
#>