# RowGroupingProtocol A type that represents a collection of row selections that have the same value in a column. ``` protocol RowGroupingProtocol : CustomStringConvertible ``` ## Topics ### Inspecting a Row Grouping [`var count: Int`](/documentation/TabularData/RowGroupingProtocol/count) The number of groups in the row grouping. ### Transforming a Row Grouping [`func mapGroups((DataFrame.Slice) throws -> DataFrame) rethrows -> Self`](/documentation/TabularData/RowGroupingProtocol/mapGroups(_:)) Generates a row grouping that applies a transformation closure to each group in the original. ### Splitting a Row Grouping [`func randomSplit(by: Double) -> (Self, Self)`](/documentation/TabularData/RowGroupingProtocol/randomSplit(by:)) Generates two row groupings by randomly splitting the original with a proportion. [`func randomSplit(by: Double, seed: Int?) -> (Self, Self)`](/documentation/TabularData/RowGroupingProtocol/randomSplit(by:seed:)) Generates two row groupings by randomly splitting the original by a proportion. ### Aggregating a Row Grouping [`func counts() -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/counts()) Generates a data frame with two columns, one that has a row for each group key and another for the number of rows in the group. [`func counts(order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/counts(order:)) Generates a data frame, that you choose how to sort, with two columns, one that has a row for each group key and another for the number or rows in the group. [`func sums(String, N.Type, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/sums(_:_:order:)) Generates a data frame that contains the sum of each group’s rows along a column you select by name. [`func sums(ColumnID, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/sums(_:order:)) Generates a data frame that contains the sum of each group’s rows along a column you select by column identifier. [`func means(String, N.Type, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/means(_:_:order:)) Generates a data frame that contains the average mean of each group’s rows along a column you select by name. [`func means(ColumnID, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/means(_:order:)) Generates a data frame that contains the average mean of each group’s rows along a column you select by column identifier. [`func minimums(String, N.Type, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/minimums(_:_:order:)) Generates a data frame that contains the minimums of each group’s rows along a column you select by name. [`func minimums(ColumnID, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/minimums(_:order:)) Generates a data frame that contains the minimums of each group’s rows along a column you select by column identifier. [`func maximums(String, N.Type, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/maximums(_:_:order:)) Generates a data frame that contains the maximums of each group’s rows along a column you select by name. [`func maximums(ColumnID, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/maximums(_:order:)) Generates a data frame that contains the maximums of each group’s rows along a column you select by column identifier. [`func aggregated(on: ColumnID, into: String?, transform: (DiscontiguousColumnSlice) throws -> Result) rethrows -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/aggregated(on:into:transform:)) Generates a data frame with a column for the group identifier and a column of values from the transform. [`func aggregated(on: [String], naming: (String) -> String, transform: (DiscontiguousColumnSlice) throws -> Result?) rethrows -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/aggregated(on:naming:transform:)) Generates a data frame by aggregating each group’s contents for each column you select by name. ### Flattening a Row Grouping [`func ungrouped() -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/ungrouped()) Generates a data frame that contains all the rows from each group in the row grouping. ### Summarizing a Row Grouping [`func summary() -> any GroupSummaries`](/documentation/TabularData/RowGroupingProtocol/summary()) Generates a group summaries instance of the row grouping’s columns. [`func summary(of: [String]) -> any GroupSummaries`](/documentation/TabularData/RowGroupingProtocol/summary(of:)) Generates a group summaries instance of the row grouping’s columns you select by name. [`protocol GroupSummaries`](/documentation/TabularData/GroupSummaries) A collection of group summaries. ### Instance Methods [`func filter((DataFrame.Slice) throws -> Bool) rethrows -> Self`](/documentation/TabularData/RowGroupingProtocol/filter(_:)) Returns a row grouping containing only the groups that satisfy a predicate. [`func quantiles(String, N.Type, quantile: N, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/quantiles(_:_:quantile:order:)) Generates a data frame that contains the quantile of each group’s rows along a column you select by name. [`func quantiles(ColumnID, quantile: N, order: Order?) -> DataFrame`](/documentation/TabularData/RowGroupingProtocol/quantiles(_:quantile:order:)) Generates a data frame that contains the quantiles of each group’s rows along a column you select by column identifier. ### Subscripts [`subscript(Any?...) -> DataFrame.Slice?`](/documentation/TabularData/RowGroupingProtocol/subscript(_:)) Retrieves a group slice by key. ## Relationships ### Conforming Types [`RowGrouping`](/documentation/TabularData/RowGrouping) ### Inherits From [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) --- 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)