# Column A column in a data frame. ``` struct Column ``` ## Overview A column is a that contains values of a specific type, including: - - - Each element in a column is an of the column’s type. Each `nil` element represents a missing value. ## Topics ### Creating a Column [`init(name:capacity:)`](/documentation/TabularData/Column/init(name:capacity:)) Creates a column with a name and a capacity. [`init(_:capacity:)`](/documentation/TabularData/Column/init(_:capacity:)) Creates a column with a column identifier and a capacity. [`init(name:contents:)`](/documentation/TabularData/Column/init(name:contents:)-6okx3) Creates a column with a name and a sequence of nonoptional values. [`init(name:contents:)`](/documentation/TabularData/Column/init(name:contents:)-8nxtj) Creates a column with a name and a sequence of optional values. [`init(_:contents:)`](/documentation/TabularData/Column/init(_:contents:)-1871a) Creates a column with an identifier and a sequence of nonoptional values. [`init(_:contents:)`](/documentation/TabularData/Column/init(_:contents:)-7z5ji) Creates a column with a column identifier and a sequence of optional values. [`init(_:)`](/documentation/TabularData/Column/init(_:)) Creates a column from a column slice. ### Creating a Column of the Same Type [`prototype`](/documentation/TabularData/Column/prototype) A prototype that creates type-erased columns with the same underlying type as the column slice. ### Creating a Type-Erased Column [`eraseToAnyColumn()`](/documentation/TabularData/Column/eraseToAnyColumn()) Generates a type-erased copy of the column. ### Creating Transformed Columns [`map(_:)`](/documentation/TabularData/Column/map(_:)) Creates a new column by applying a transformation to every element. [`mapNonNil(_:)`](/documentation/TabularData/Column/mapNonNil(_:)) Creates a new column by applying the transformation to every element that isn’t missing. ### Inspecting a Column [`name`](/documentation/TabularData/Column/name) The name of the column. [`count`](/documentation/TabularData/Column/count) The number of elements in the column. [`missingCount`](/documentation/TabularData/Column/missingCount) The number of missing elements in the column. [`Column.Element`](/documentation/TabularData/Column/Element) The type of the column’s elements, which is an optional type of the column’s type. [`wrappedElementType`](/documentation/TabularData/Column/wrappedElementType) The underlying type of the column’s elements. ### Transforming a Column [`transform(_:)`](/documentation/TabularData/Column/transform(_:)-271dd) Applies a transformation to every element that isn’t missing. [`transform(_:)`](/documentation/TabularData/Column/transform(_:)-6mrwg) Applies a transformation to every element in the column. ### Adding Elements [`append(_:)`](/documentation/TabularData/Column/append(_:)-qycj) Appends a nonoptional value to the column. [`append(_:)`](/documentation/TabularData/Column/append(_:)-4t2pt) Appends an optional value to the column. [`append(contentsOf:)`](/documentation/TabularData/Column/append(contentsOf:)-qb4p) Appends a sequence of nonoptional values to the column. [`append(contentsOf:)`](/documentation/TabularData/Column/append(contentsOf:)-42y1d) Appends a sequence of optional values to the column. ### Finding an Element Index [`argmin()`](/documentation/TabularData/Column/argmin()) Returns the index of the element with the lowest value, ignoring missing elements. [`argmax()`](/documentation/TabularData/Column/argmax()) Returns the index of the element with the highest value, ignoring missing elements. ### Removing an Element [`remove(at:)`](/documentation/TabularData/Column/remove(at:)) Removes an element from the column. ### Accessing Elements [`subscript(_:)`](/documentation/TabularData/Column/subscript(_:)-qm4d) Accesses an element at an index. [`subscript(_:)`](/documentation/TabularData/Column/subscript(_:)-52xy1) Accesses a contiguous range of elements with a range expression. [`subscript(_:)`](/documentation/TabularData/Column/subscript(_:)-gne9) Accesses a contiguous range of elements. ### Creating a Slice of Unique Elements [`distinct()`](/documentation/TabularData/Column/distinct()) Generates a discontiguous slice that contains unique elements. ### Creating a Slice by Masking Elements [`subscript(_:)`](/documentation/TabularData/Column/subscript(_:)-56i2s) Returns a column slice that includes elements that correspond to a collection of Booleans. ### Encoding a Column [`encoded(using:)`](/documentation/TabularData/Column/encoded(using:)) Generates a column by encoding each element’s value. ### Decoding a Column [`decoded(_:using:)`](/documentation/TabularData/Column/decoded(_:using:)) Generates a column by decoding each element’s data. ### Summarizing a Column [`summary()`](/documentation/TabularData/Column/summary()) Generates a categorical summary of the column’s elements. [`numericSummary()`](/documentation/TabularData/Column/numericSummary()-2m0sr) Generates a numeric summary of the integer column’s elements. [`numericSummary()`](/documentation/TabularData/Column/numericSummary()-8laeo) Generates a numeric summary of the floating-point column’s elements. ### Getting Statistical Values [`sum()`](/documentation/TabularData/Column/sum()) Returns the sum of the column’s elements, ignoring missing elements. [`min()`](/documentation/TabularData/Column/min()) Returns the element with the lowest value, ignoring missing elements. [`max()`](/documentation/TabularData/Column/max()) Returns the element with the highest value, ignoring missing elements. [`mean()`](/documentation/TabularData/Column/mean()-2si7j) Returns the mean average of the integer column’s elements, ignoring missing elements. [`mean()`](/documentation/TabularData/Column/mean()-ic5z) Returns the mean average of the floating-point column’s elements, ignoring missing elements. [`standardDeviation(deltaDegreesOfFreedom:)`](/documentation/TabularData/Column/standardDeviation(deltaDegreesOfFreedom:)-9ffqu) Returns the standard deviation of the integer column’s elements, ignoring missing elements. [`standardDeviation(deltaDegreesOfFreedom:)`](/documentation/TabularData/Column/standardDeviation(deltaDegreesOfFreedom:)-4kc16) Returns the standard deviation of the floating-point column’s elements, ignoring missing elements. ### Describing a Column [`description`](/documentation/TabularData/Column/description) A text representation of the column. [`debugDescription`](/documentation/TabularData/Column/debugDescription) A text representation of the column suitable for debugging. [`customMirror`](/documentation/TabularData/Column/customMirror) A mirror that reflects the column. ### Comparing Two Columns ### Modifying a Column with a Value [`+=(_:_:)`](/documentation/TabularData/Column/+=(_:_:)-94q8g) Modifies a column by adding a value to each element. [`-=(_:_:)`](/documentation/TabularData/Column/-=(_:_:)-8arlr) Modifies a column by subtracting a value from each element. [`*=(_:_:)`](/documentation/TabularData/Column/*=(_:_:)-4rraw) Modifies a column by multiplying each element by a value. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-8jmir) Modifies an integer column by dividing each element by a value. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-3hfr5) Modifies a floating-point column by dividing each element by a value. ### Modifying a Column with a Collection of Values [`+=(_:_:)`](/documentation/TabularData/Column/+=(_:_:)-2w5o4) Modifies a column by adding each value in a collection to the corresponding element in the column. [`+=(_:_:)`](/documentation/TabularData/Column/+=(_:_:)-2scuy) Modifies a column by adding each optional value in a collection to the corresponding element in the column. [`-=(_:_:)`](/documentation/TabularData/Column/-=(_:_:)-8rgjq) Modifies a column by subtracting each value in a collection from the corresponding element in the column. [`-=(_:_:)`](/documentation/TabularData/Column/-=(_:_:)-3v0hh) Modifies a column by subtracting each optional value in a collection from the corresponding element in the column. [`*=(_:_:)`](/documentation/TabularData/Column/*=(_:_:)-8mmnn) Modifies a column by multiplying each element in the column by the corresponding value in a collection. [`*=(_:_:)`](/documentation/TabularData/Column/*=(_:_:)-6kp11) Modifies a column by multiplying each element in the column by the corresponding optional value in a collection. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-dnma) Modifies an integer column by dividing each element in the column by the corresponding value in a collection. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-8xhzg) Modifies an integer column by dividing each element in the column by the corresponding optional value in a collection. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-86t1j) Modifies a floating-point column by dividing each element in the column by the corresponding value in a collection. [`/=(_:_:)`](/documentation/TabularData/Column/_=(_:_:)-3acz8) Modifies a floating-point column by dividing each element in the column by the corresponding optional value in a collection. ### Generating a Column by Combining Two Columns ### 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 ### Supporting Types ### Invoking Protocol Methods --- Copyright © 2026 Apple Inc. 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