Get or set a slice of an array

rray_slice() is a shortcut wrapper around rray_subset() that is useful for easily subsetting along a single axis.

rray_slice(x, i, axis) <- value

rray_slice_assign(x, i, axis, value)

rray_slice(x, i, axis)

Arguments

x	A vector, matrix, array or rray.
i	Indices to extract along a single axis. Integer indices extract specific elements of the axis dimension. Logical indices must be length 1, or the length of the axis dimension. Character indices are only allowed if x has names for the axis dimension. NULL is treated as 0.
axis	An integer. The axis to subset along.
value	A value to be assigned to the location at rray_slice(x, i, axis). It will be cast to the type and dimension of the slice of x.

Value

x with the i elements extracted from the axis.

Details

rray_slice() does exactly the same thing as rray_subset(), and is mainly helpful for higher dimensional objects, when you need to subset along, for example, only the 4th dimension.

See also

Other rray subsetters: rray_extract<-, rray_subset<-, rray_yank<-

Examples

x <- rray(1:16, c(2, 2, 2, 2))

# Selecting the first column
rray_slice(x, i = 1, axis = 2)
#> <rray<int>[,1,2,2][2]>
#> , , 1, 1
#> 
#>      [,1]
#> [1,]    1
#> [2,]    2
#> 
#> , , 2, 1
#> 
#>      [,1]
#> [1,]    5
#> [2,]    6
#> 
#> , , 1, 2
#> 
#>      [,1]
#> [1,]    9
#> [2,]   10
#> 
#> , , 2, 2
#> 
#>      [,1]
#> [1,]   13
#> [2,]   14
#> 

# rray_slice() is particularly useful for
# subsetting higher dimensions because you don't
# have to worry about the commas
rray_slice(x, i = 2, axis = 4)
#> <rray<int>[,2,2,1][2]>
#> , , 1, 1
#> 
#>      [,1] [,2]
#> [1,]    9   11
#> [2,]   10   12
#> 
#> , , 2, 1
#> 
#>      [,1] [,2]
#> [1,]   13   15
#> [2,]   14   16
#> 

# Compare the above with the equivalent using `[`
x[, , , 2]
#> <rray<int>[,2,2,1][2]>
#> , , 1, 1
#> 
#>      [,1] [,2]
#> [1,]    9   11
#> [2,]   10   12
#> 
#> , , 2, 1
#> 
#>      [,1] [,2]
#> [1,]   13   15
#> [2,]   14   16
#> 

# `i` can be a character vector if `x` has names along `axis`
x <- rray_set_axis_names(x, axis = 4, c("foo", "bar"))
rray_slice(x, "bar", axis = 4)
#> <rray<int>[,2,2,1][2]>
#> , , 1, bar
#> 
#>      [,1] [,2]
#> [1,]    9   11
#> [2,]   10   12
#> 
#> , , 2, bar
#> 
#>      [,1] [,2]
#> [1,]   13   15
#> [2,]   14   16
#> 

# The assignment variation can be useful
# for assigning to higher dimensional elements
rray_slice(x, 1, 3) <- matrix(c(99, 100), nrow = 1)