All()

Select all columns.

Between(first, last)

Select the columns between first and last (including both) from a table.

BroadcastedSelector(selector)

Wrapper type around a Between, All or Cols indicating that an operation should be applied to each column included by the wrapped selector.

Examples

julia> using DataAPI

julia> DataAPI.Between(:a, :e) .=> sin
DataAPI.BroadcastedSelector{DataAPI.Between{Symbol, Symbol}}(DataAPI.Between{Symbol, Symbol}(:a, :e)) => sin

julia> DataAPI.Cols(r"x") .=> [sum, prod]
2-element Vector{Pair{DataAPI.BroadcastedSelector{DataAPI.Cols{Tuple{Regex}}}, _A} where _A}:
 DataAPI.BroadcastedSelector{DataAPI.Cols{Tuple{Regex}}}(DataAPI.Cols{Tuple{Regex}}((r"x",))) => sum
 DataAPI.BroadcastedSelector{DataAPI.Cols{Tuple{Regex}}}(DataAPI.Cols{Tuple{Regex}}((r"x",))) => prod

Cols(cols...; operator=union)
Cols(f::Function; operator=union)

Select columns matching specifications in cols. If cols == (), select no columns.

If the only positional argument is a Function f then select the columns whose names passed to the f predicate as strings return true.

When multiple cols selectors are passed then the sets of columns selected by them are passed to operator as positional arguments. operator should be a set operation function, like union, intersect, setdiff, and symdiff defined in Base Julia. By default operator=union in which case all columns matching at least one selector are returned.

allcombinations(sink, ...)

Create table from all combinations of values in passed arguments using a sink function to materialize the table.

colmetadata(x, col, key::AbstractString, [default]; style::Bool=false)

Return metadata value associated with table x for column col and key key. Throw an error if x does not support reading metadata for column col or x supports reading metadata, but does not have a mapping for column col for key.

col must have a type that is supported by table x for column indexing. Following the Tables.jl contract Symbol and Int are always allowed. Throw an error if col is not a column of x.

If style=true return a tuple of metadata value and metadata style. Metadata style is an additional information about the kind of metadata that is stored for the key.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

If default is passed then return it if x supports reading metadata and has column col but mapping for key is missing. If style=true return (default, :default).

colmetadata!(x, col, key::AbstractString, value; style::Symbol=:default)

Set metadata for table x for column col for key key to have value value and style style (:default by default) and return x. Throw an error if x does not support setting metadata for column col.

col must have a type that is supported by table x for column indexing. Following the Tables.jl contract Symbol and Int are always allowed. Throw an error if col is not a column of x.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

colmetadata(x, [col]; style::Bool=false)

If col is not passed return a dictionary mapping columns represented as Symbol that have associated metadata to dictionaries mapping all metadata keys to metadata values associated with table x for a given column.

If col is passed return a dictionary mapping all column metadata keys to metadata values associated with column col of table x. Throw an error if x does not support reading metadata for column col or column col is not present in x.

If style=true values are tuples of metadata value and metadata style. Metadata style is an additional information about the kind of metadata that is stored for the key.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

The returned dictionary may be freshly allocated on each call to colmetadata and is considered to be owned by x so it must not be modified.

colmetadatakeys(x, [col])

If col is passed return an iterator of metadata keys for which metadata(x, col, key) returns a metadata value. Throw an error if x does not support reading column metadata or if col is not a column of x.

col must have a type that is supported by table x for column indexing. Following the Tables.jl contract Symbol and Int are always allowed.

If col is not passed return an iterator of col => colmetadatakeys(x, col) pairs for all columns that have metadata, where col are Symbol. If x does not support column metadata return ().

colmetadatasupport(T::Type)

Return a NamedTuple{(:read, :write), Tuple{Bool, Bool}} indicating whether values of type T support column metadata.

The read field indicates whether reading metadata with the colmetadata and colmetadatakeys functions is supported.

The write field indicates whether modifying metadata with the colmetadata!, deletecolmetadata!, and emptycolmetadata! functions is supported.

defaultarray(T, N)

For a given element type T and number of dimensions N, return the appropriate array type.

The default definition returns Array{T, N}. This function is useful for custom types that have a more efficient vectorized representation (usually using SOA optimizations).

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.

deletecolmetadata!(x, col, key::AbstractString)

Delete metadata for table x for column col for key key and return x (if metadata for key is not present do not perform any action). Throw an error if x does not support metadata deletion for column col.

deletemetadata!(x, key::AbstractString)

Delete metadata for object x for key key and return x (if metadata for key is not present do not perform any action). Throw an error if x does not support metadata deletion.

describe(io::IO, x)

For an object x, print descriptive statistics to io.

This generic function is owned by StatsBase.jl, which is the sole provider of the default definition.

emptycolmetadata!(x, [col])

Delete all metadata for table x for column col. If col is not passed delete all column level metadata for table x. Throw an error if x does not support metadata deletion for column col.

emptymetadata!(x)

Delete all metadata for object x. Throw an error if x does not support metadata deletion.

invrefpool(A)

Whenever available, return an indexable object such that given an array A for which refpool(A) is not nothing:

• for any valid index x into refpool(A), invrefpool(A)[refpool(A)[x]] is equal to x (according to isequal) and of the same type as x;
• for any valid index ix into invrefpool(A) , refpool(A)[invrefpool(A)[ix]] is equal to ix (according to isequal) and of the same type as ix.

Additionally it is required that for invrefpool(A) the following methods are defined:

• Base.haskey: allowing to check if ix is a valid index into it.
• Base.get: allowing to get a value from it or a passed default value if it is not present.

By default, invrefpool(A) returns nothing.

If invrefpool(A) is not nothing, then refpool(A) also must not be nothing.

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.

levels(x; skipmissing=true)

Return a vector of unique values which occur or could occur in collection x. missing values are skipped unless skipmissing=false is passed.

Values are returned in the preferred order for the collection, with the result of sort as a default. If the collection is not sortable then the order of levels is unspecified.

Contrary to unique, this function may return values which do not actually occur in the data, and does not preserve their order of appearance in x.

metadata(x, key::AbstractString, [default]; style::Bool=false)

Return metadata value associated with object x for key key. Throw an error if x does not support reading metadata or does not have a mapping for key.

If style=true return a tuple of metadata value and metadata style. Metadata style is an additional information about the kind of metadata that is stored for the key.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

If default is passed then return it if reading metadata is supported but mapping for key is missing. If style=true return (default, :default).

metadata!(x, key::AbstractString, value; style::Symbol=:default)

Set metadata for object x for key key to have value value and style style (:default by default) and return x. Throw an error if x does not support setting metadata.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

metadata(x; style::Bool=false)

Return a dictionary mapping all metadata keys to metadata values associated with object x. Throw an error if x does not support reading metadata.

If style=true values are tuples of metadata value and metadata style. Metadata style is an additional information about the kind of metadata that is stored for the key.

One of the uses of the metadata style is decision how the metadata should be propagated when x is transformed. This interface defines the :default style that indicates that metadata should not be propagated under any operations (it is only preserved when a copy of the source table is performed). All types supporting metadata allow at least this style.

The returned dictionary may be freshly allocated on each call to metadata and is considered to be owned by x so it must not be modified.

metadatakeys(x)

Return an iterator of metadata keys for which metadata(x, key) returns a metadata value. Throw an error if x does not support reading metadata.

metadatasupport(T::Type)

Return a NamedTuple{(:read, :write), Tuple{Bool, Bool}} indicating whether values of type T support metadata.

The read field indicates whether reading metadata with the metadata and [metadatakeys]](@ref) functions is supported.

The write field indicates whether modifying metadata with the metadata!, deletemetadata!, and emptymetadata! functions is supported.

ncol(t)

Return the number of columns of table t.

nrow(t)

Return the number of rows of table t.

refarray(A::AbstractArray)

For a given array A, potentially return an optimized "ref array" representation of the original array, which can allow for faster comparison and sorting.

The default definition just returns the input array. This function is useful for custom array types which already store a "hashed"-like representation of elements where testing equality or permuting elements in place can be much faster than the original scalar value, like pooled arrays.

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.

refpool(A)

Whenever available, return an indexable object pool such that, given the original array A and a "ref value" x taken from refarray(A), pool[x] is the appropriate original value. Return nothing if such object is not available.

By default, refpool(A) returns nothing.

If refpool(A) is not nothing, then refpool(A)[refarray(A)[I...]] must be equal to (according to isequal) and of the same type as A[I...], and the object returned by refpool(A) must implement the iteration and indexing interfaces as well as the length, eachindex, keys, values, pairs, firstindex, lastindex, and eltype functions in accordance with the AbstractArray interface.

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.

refvalue(A, x)

For the original array A, and a "ref value" x taken from refarray(A), return the appropriate original value. refvalue(A, refarray(A)[I...]) must be equal to A[I...].

By default, refvalue(A, x) returns x (since refarray(A) returns A by default). This allows recovering an original array element after operating on the "ref values".

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.

rownumber(row)

Return the row number of row in the source table.

unwrap(x)

For a given scalar argument x, potentially "unwrap" it to return the base wrapped value. Useful as a generic API for wrapper types when the original value is needed.

The default definition just returns x itself, i.e. no unwrapping is performned.

This generic function is owned by DataAPI.jl itself, which is the sole provider of the default definition.