# ColumnSlice A collection that represents a selection of contiguous elements from a typed column. ``` struct ColumnSlice ``` ## Overview A column slice contains only certain elements from its parent column. Create a slice by using a subscript with a range. ```swift let slice = column[100 ..< 200] ``` ## Topics ### Creating a Column Slice [`init(Column)`](/documentation/TabularData/ColumnSlice/init(_:)) Creates a slice with the contents of a column. ### Creating a Slice of Unique Elements [`func distinct() -> DiscontiguousColumnSlice`](/documentation/TabularData/ColumnSlice/distinct()) Generates a discontiguous slice that contains unique elements. ### Creating a Type-Erased Slice [`func eraseToAnyColumn() -> AnyColumnSlice`](/documentation/TabularData/ColumnSlice/eraseToAnyColumn()) Returns a type-erased column slice. ### Creating a Column of the Same Type [`var prototype: any AnyColumnPrototype`](/documentation/TabularData/ColumnSlice/prototype) A prototype that creates type-erased columns with the same underlying type as the column slice. ### Creating Transformed Columns [`func map((ColumnSlice.Element) throws -> T?) rethrows -> Column`](/documentation/TabularData/ColumnSlice/map(_:)) Creates a new column by applying a transformation to every element. ### Inspecting a Column Slice [`var name: String`](/documentation/TabularData/ColumnSlice/name) The name of the slice’s parent column. [`var count: Int`](/documentation/TabularData/ColumnSlice/count) The number of elements in the column slice. [`var wrappedElementType: any Any.Type`](/documentation/TabularData/ColumnSlice/wrappedElementType) The underlying type of the column’s elements. [`func argmin() -> Int?`](/documentation/TabularData/ColumnSlice/argmin()) Returns the index of the element with the lowest value, ignoring missing elements. [`func argmax() -> Int?`](/documentation/TabularData/ColumnSlice/argmax()) Returns the index of the element with the highest value, ignoring missing elements. [`func isNil(at: Int) -> Bool`](/documentation/TabularData/ColumnSlice/isNil(at:)) Returns a Boolean that indicates whether the element at an index is missing. ### Accessing Elements [`subscript(Int) -> ColumnSlice.Element`](/documentation/TabularData/ColumnSlice/subscript(_:)-38hn8) Accesses an element at an index. [`subscript(Range) -> ColumnSlice`](/documentation/TabularData/ColumnSlice/subscript(_:)-7lrhk) Accesses a contiguous range of elements. ### Summarizing a Column Slice [`func summary() -> CategoricalSummary`](/documentation/TabularData/ColumnSlice/summary()) Generates a categorical summary of the column slice’s elements. [`func numericSummary() -> NumericSummary`](/documentation/TabularData/ColumnSlice/numericSummary()-68ohj) Generates a numeric summary of the integer column slice’s elements. [`func numericSummary() -> NumericSummary`](/documentation/TabularData/ColumnSlice/numericSummary()-5swa5) Generates a numeric summary of the floating-point column slice’s elements. ### Getting Statistical Values [`func sum() -> WrappedElement`](/documentation/TabularData/ColumnSlice/sum()) Returns the sum of the column slice’s elements, ignoring missing elements. [`func min() -> ColumnSlice.Element`](/documentation/TabularData/ColumnSlice/min()) Returns the element with the lowest value, ignoring missing elements. [`func max() -> ColumnSlice.Element`](/documentation/TabularData/ColumnSlice/max()) Returns the element with the highest value, ignoring missing elements. [`func mean() -> Double?`](/documentation/TabularData/ColumnSlice/mean()-3inzf) Returns the mean average of the integer slice’s elements, ignoring missing elements. [`func mean() -> ColumnSlice.Element`](/documentation/TabularData/ColumnSlice/mean()-7u3i0) Returns the mean average of the floating-point slice’s elements, ignoring missing elements. [`func standardDeviation(deltaDegreesOfFreedom: Int) -> Double?`](/documentation/TabularData/ColumnSlice/standardDeviation(deltaDegreesOfFreedom:)-1i05i) Returns the standard deviation of the integer column slice’s elements, ignoring missing elements. [`func standardDeviation(deltaDegreesOfFreedom: Int) -> ColumnSlice.Element`](/documentation/TabularData/ColumnSlice/standardDeviation(deltaDegreesOfFreedom:)-3d6vo) Returns the standard deviation of the floating-point column slice’s elements, ignoring missing elements. ### Describing a Column Slice [`var description: String`](/documentation/TabularData/ColumnSlice/description) A text representation of the column slice. [`var debugDescription: String`](/documentation/TabularData/ColumnSlice/debugDescription) A text representation of the column slice suitable for debugging. [`var customMirror: Mirror`](/documentation/TabularData/ColumnSlice/customMirror) A mirror that reflects the column slice. ### Comparing Two Column Slices [`static func == (ColumnSlice, ColumnSlice) -> Bool`](/documentation/TabularData/ColumnSlice/==(_:_:)) Returns a Boolean that indicates whether the column slices are equal. ### Modifying a Column Slice with a Value [`static func += (inout ColumnSlice, WrappedElement)`](/documentation/TabularData/ColumnSlice/+=(_:_:)-950qi) Modifies a column slice by adding a value to each element. [`static func -= (inout ColumnSlice, WrappedElement)`](/documentation/TabularData/ColumnSlice/-=(_:_:)-1n1gh) Modifies a column slice by subtracting a value from each element. [`static func *= (inout ColumnSlice, WrappedElement)`](/documentation/TabularData/ColumnSlice/*=(_:_:)-i6qs) Modifies a column slice by multiplying each element by a value. [`static func /= (inout ColumnSlice, WrappedElement)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-8oi36) Modifies an integer column slice by dividing each element by a value. [`static func /= (inout ColumnSlice, WrappedElement)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-8pl3f) Modifies a floating-point column slice by dividing each element by a value. ### Modifying a Column Slice with a Collection of Values [`static func += (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/+=(_:_:)-47cwm) Modifies a column slice by adding each value in a collection to the corresponding element in the column. [`static func += (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/+=(_:_:)-4bgdt) Modifies a column slice by adding each optional value in a collection to the corresponding element in the column. [`static func -= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/-=(_:_:)-3kauw) Modifies a column slice by subtracting each value in a collection from the corresponding element in the column. [`static func -= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/-=(_:_:)-1bqy4) Modifies a column slice by subtracting each optional value in a collection from the corresponding element in the column. [`static func *= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/*=(_:_:)-7lz8l) Modifies a column slice by multiplying each element in the column by the corresponding value in a collection. [`static func *= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/*=(_:_:)-3v2q0) Modifies a column slice by multiplying each element in the column by the corresponding optional value in a collection. [`static func /= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-46jci) Modifies an integer column slice by dividing each element in the column by the corresponding value in a collection. [`static func /= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-8frqe) Modifies an integer column slice by dividing each element in the column by the corresponding optional value in a collection. [`static func /= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-1fciw) Modifies a floating-point column slice by dividing each element in the column by the corresponding value in a collection. [`static func /= (inout ColumnSlice, C)`](/documentation/TabularData/ColumnSlice/_=(_:_:)-6ujes) Modifies a floating-point column slice by dividing each element in the column by the corresponding optional value in a collection. ### Generating a Column by Combining Two Column Slices ### Generating a Column by Adding a Value ### Generating a Column by Subtracting a Value ### Generating a Column by Multiplying a Value ### Generating a Column by Dividing a Value ### Hashing a Column Slice [`func hash(into: inout Hasher)`](/documentation/TabularData/ColumnSlice/hash(into:)) Hashes the essential components of the column slice by feeding them into a hasher. ### Supporting Types [`typealias Element`](/documentation/TabularData/ColumnSlice/Element) The type of the column slice’s elements, which is an optional type of the parent column’s type. [`typealias Index`](/documentation/TabularData/ColumnSlice/Index) The type that represents a position in the column slice. ### Invoking Protocol Methods ### Instance Properties [`var missingCount: Int`](/documentation/TabularData/ColumnSlice/missingCount) The number of missing elements in the column slice. ### Default Implementations [BidirectionalCollection Implementations](/documentation/TabularData/ColumnSlice/BidirectionalCollection-Implementations) [Collection Implementations](/documentation/TabularData/ColumnSlice/Collection-Implementations) [CustomDebugStringConvertible Implementations](/documentation/TabularData/ColumnSlice/CustomDebugStringConvertible-Implementations) [CustomReflectable Implementations](/documentation/TabularData/ColumnSlice/CustomReflectable-Implementations) [CustomStringConvertible Implementations](/documentation/TabularData/ColumnSlice/CustomStringConvertible-Implementations) [Equatable Implementations](/documentation/TabularData/ColumnSlice/Equatable-Implementations) [Hashable Implementations](/documentation/TabularData/ColumnSlice/Hashable-Implementations) ## Relationships ### Conforms To [`BidirectionalCollection`](/documentation/Swift/BidirectionalCollection) [`Sendable`](/documentation/Swift/Sendable) [`Equatable`](/documentation/Swift/Equatable) [`Hashable`](/documentation/Swift/Hashable) [`Collection`](/documentation/Swift/Collection) [`Escapable`](/documentation/Swift/Escapable) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`OptionalColumnProtocol`](/documentation/TabularData/OptionalColumnProtocol) [`RandomAccessCollection`](/documentation/Swift/RandomAccessCollection) [`MutableCollection`](/documentation/Swift/MutableCollection) [`CustomReflectable`](/documentation/Swift/CustomReflectable) [`Sequence`](/documentation/Swift/Sequence) [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) [`ColumnProtocol`](/documentation/TabularData/ColumnProtocol) [`Copyable`](/documentation/Swift/Copyable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)