aperm_array_to_vector: Permute an R array to a linear vector of data

In ctypesio: Read and Write Standard 'C' Types from Files, Connections and Raw Vectors

Permute an R array to a linear vector of data

Description

Permute an R array to a linear vector of data

Usage

aperm_array_to_vector(x, dst, flipy = FALSE)

Arguments

x	array
dst	Specification of destination dimensions in the order of presentation in the source data. Character vector which contains 3 strings: 'planes', 'rows', 'cols'. The order of these strings determines the order of output in the linear data. Currently, "planes" must always be the final element.
flipy	flip the array vertically. Default: FALSE

Value

vector

See Also

Other data permutation functions: aperm_vector_to_array(), flip_endian()

Examples

# create a small RGBA array in R with each 
# plane of the array holding a different colour channel
  arr <- array(c(paste0('r', 1:6), 
                 paste0('g', 1:6), 
                 paste0('b', 1:6),
                 paste0('a', 1:6)), c(2, 3, 4))
arr

# A very common C ordering is packaged RGBA data in column major format
# i.e. Iterate over: planes, then columns, then rows
# i.e. 
#    start at first element
#    (plane1, plane2, plane3, plane4)
#    go to next column
#    (plane1, plane2, plane3, plane4)
#    go to next column
#    ...
#    when last column is done
#    do to next row

# Convert to packed RGBA in column-major format
vec <- aperm_array_to_vector(arr, dst = c('planes', 'cols', 'rows'))
vec

# To convert column-major packed RGBA to an R array, use the same ordering
# for the dimensions, but also need to specify length along each dimension
aperm_vector_to_array(vec, src = c(planes = 4, cols = 3, rows = 2))

ctypesio documentation built on April 3, 2025, 7:28 p.m.