Arrow Arrays

An Array is an immutable data array with some logical type and some length. Most logical types are contained in the base Array class; there are also subclasses for DictionaryArray, ListArray, and StructArray.

Factory

The Array$create() factory method instantiates an Array and takes the following arguments:

• x: an R vector, list, or data.frame

• type: an optional data type for x. If omitted, the type will be inferred from the data.

Array$create() will return the appropriate subclass of Array, such as DictionaryArray when given an R factor.

To compose a DictionaryArray directly, call DictionaryArray$create(), which takes two arguments:

• x: an R vector or Array of integers for the dictionary indices

• dict: an R vector or Array of dictionary values (like R factor levels but not limited to strings only)

Usage

a <- Array$create(x)
length(a)

print(a)
a == a

Methods

• $IsNull(i): Return true if value at index is null. Does not boundscheck

• $IsValid(i): Return true if value at index is valid. Does not boundscheck

• $length(): Size in the number of elements this array contains

• $offset(): A relative position into another array's data, to enable zero-copy slicing

• $null_count(): The number of null entries in the array

• $type(): logical type of data

• $type_id(): type id

• $Equals(other) : is this array equal to other

• $ApproxEquals(other) :

• $data(): return the underlying ArrayData

• $as_vector(): convert to an R vector

• $ToString(): string representation of the array

• $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 an Array with values at positions given by integers (R vector or Array Array) i.

• $Filter(i, keep_na = TRUE): return an Array with values at positions where logical vector (or Arrow boolean Array) i is TRUE.

• $RangeEquals(other, start_idx, end_idx, other_start_idx) :

• $cast(target_type, safe = TRUE, options = cast_options(safe)): Alter the data in the array to change its type.

• $View(type): Construct a zero-copy view of this array 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)