A ChunkedArray is a data structure managing a list of
primitive Arrow Arrays logically as one large array. Chunked arrays
may be grouped together in a Table.
chunked_array(..., type = NULL)Vectors to coerce
currently ignored
The ChunkedArray$create() factory method instantiates the object from
various Arrays or R vectors. chunked_array() is an alias for it.
$length(): Size in the number of elements this array contains
$chunk(i): Extract an Array chunk by integer position
`$nbytes() : Total number of bytes consumed by the elements of the array
$as_vector(): convert to an R vector
$Slice(offset, length = NULL): Construct a zero-copy slice of the array
with the indicated offset and length. If length is NULL, the slice goes
until the end of the array.
$Take(i): return a ChunkedArray with values at positions given by
integers i. If i is an Arrow Array or ChunkedArray, it will be
coerced to an R vector before taking.
$Filter(i, keep_na = TRUE): return a ChunkedArray with values at positions where
logical vector or Arrow boolean-type (Chunked)Array i is TRUE.
$SortIndices(descending = FALSE): return an Array of integer positions that can be
used to rearrange the ChunkedArray in ascending or descending order
$cast(target_type, safe = TRUE, options = cast_options(safe)): Alter the
data in the array to change its type.
$null_count: The number of null entries in the array
$chunks: return a list of Arrays
$num_chunks: integer number of chunks in the ChunkedArray
$type: logical type of data
$View(type): Construct a zero-copy view of this ChunkedArray with the
given type.
$Validate(): Perform any validation checks to determine obvious inconsistencies
within the array's internal data. This can be an expensive check, potentially O(length)
# Pass items into chunked_array as separate objects to create chunks
class_scores <- chunked_array(c(87, 88, 89), c(94, 93, 92), c(71, 72, 73))
class_scores$num_chunks
#> [1] 3
# When taking a Slice from a chunked_array, chunks are preserved
class_scores$Slice(2, length = 5)
#> ChunkedArray
#> [
#> [
#> 89
#> ],
#> [
#> 94,
#> 93,
#> 92
#> ],
#> [
#> 71
#> ]
#> ]
# You can combine Take and SortIndices to return a ChunkedArray with 1 chunk
# containing all values, ordered.
class_scores$Take(class_scores$SortIndices(descending = TRUE))
#> ChunkedArray
#> [
#> [
#> 94,
#> 93,
#> 92,
#> 89,
#> 88,
#> 87,
#> 73,
#> 72,
#> 71
#> ]
#> ]
# If you pass a list into chunked_array, you get a list of length 1
list_scores <- chunked_array(list(c(9.9, 9.6, 9.5), c(8.2, 8.3, 8.4), c(10.0, 9.9, 9.8)))
list_scores$num_chunks
#> [1] 1
# When constructing a ChunkedArray, the first chunk is used to infer type.
doubles <- chunked_array(c(1, 2, 3), c(5L, 6L, 7L))
doubles$type
#> Float64
#> double
# Concatenating chunked arrays returns a new chunked array containing all chunks
a <- chunked_array(c(1, 2), 3)
b <- chunked_array(c(4, 5), 6)
c(a, b)
#> ChunkedArray
#> [
#> [
#> 1,
#> 2
#> ],
#> [
#> 3
#> ],
#> [
#> 4,
#> 5
#> ],
#> [
#> 6
#> ]
#> ]