Struct arrow::array::DictionaryArray [−][src]
pub struct DictionaryArray<K: ArrowPrimitiveType> { /* fields omitted */ }
Expand description
A dictionary array where each element is a single value indexed by an integer key. This is mostly used to represent strings or a limited set of primitive types as integers, for example when doing NLP analysis or representing chromosomes by name.
Example with nullable data:
use arrow::array::{DictionaryArray, Int8Array};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array : DictionaryArray<Int8Type> = test.iter().map(|&x| if x == "b" {None} else {Some(x)}).collect();
assert_eq!(array.keys(), &Int8Array::from(vec![Some(0), Some(0), None, Some(1)]));
Example without nullable data:
use arrow::array::{DictionaryArray, Int8Array};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array : DictionaryArray<Int8Type> = test.into_iter().collect();
assert_eq!(array.keys(), &Int8Array::from(vec![0, 0, 1, 2]));
Implementations
Return an array view of the keys of this dictionary as a PrimitiveArray.
Returns the lookup key by doing reverse dictionary lookup
Returns a clone of the value type of this list.
Trait Implementations
Returns a reference-counted pointer to the underlying data of this array.
Returns a zero-copy slice of this array with the indicated offset and length. Read more
Returns the offset into the underlying data used by this array(-slice).
Note that the underlying data can be shared by many arrays.
This defaults to 0
. Read more
Returns whether the element at index
is null.
When using this function on a slice, the index is relative to the slice. Read more
Returns whether the element at index
is not null.
When using this function on a slice, the index is relative to the slice. Read more
Returns the total number of null values in this array. Read more
Returns the total number of bytes of memory pointed to by this array. The buffers store bytes in the Arrow memory format, and include the data as well as the validity map. Read more
Returns the total number of bytes of memory occupied physically by this array.
This value will always be greater than returned by get_buffer_memory_size()
and
includes the overhead of the data structures that contain the pointers to the various buffers. Read more
returns two pointers that represent this array in the C Data Interface (FFI)
Constructs a DictionaryArray
from an array data reference.
impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<&'a str> for DictionaryArray<T>
impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<&'a str> for DictionaryArray<T>
Constructs a DictionaryArray
from an iterator of strings.
Example:
use arrow::array::{DictionaryArray, PrimitiveArray, StringArray};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array: DictionaryArray<Int8Type> = test.into_iter().collect();
assert_eq!(
"DictionaryArray {keys: PrimitiveArray<Int8>\n[\n 0,\n 0,\n 1,\n 2,\n] values: StringArray\n[\n \"a\",\n \"b\",\n \"c\",\n]}\n",
format!("{:?}", array)
);
Creates a value from an iterator. Read more
impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<Option<&'a str>> for DictionaryArray<T>
impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<Option<&'a str>> for DictionaryArray<T>
Constructs a DictionaryArray
from an iterator of optional strings.
Example:
use arrow::array::{DictionaryArray, PrimitiveArray, StringArray};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array: DictionaryArray<Int8Type> = test
.iter()
.map(|&x| if x == "b" { None } else { Some(x) })
.collect();
assert_eq!(
"DictionaryArray {keys: PrimitiveArray<Int8>\n[\n 0,\n 0,\n null,\n 1,\n] values: StringArray\n[\n \"a\",\n \"c\",\n]}\n",
format!("{:?}", array)
);