# 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 columnID: ColumnID, into aggregatedColumnName: String? = nil, transform: (DiscontiguousColumnSlice) throws -> Result) rethrows -> DataFrame ``` ## Parameters `columnID` A column identifier. `aggregatedColumnName` The name of the aggregation column the method adds to the data frame. `transform` A closure that transforms each group’s elements in the column. --- 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)