# subscript(_:) Creates a subset of the table by masking the rows with the given column of Booleans. ``` subscript(mask: MLDataColumn) -> MLDataTable { get } ``` ## Parameters `mask` A Boolean column indicating whether rows should be kept (`true`) or removed (`false`) in the derived table. ## Return Value A new data table. ## Overview Use this Boolean column–based subscript to create a new table by masking a subset of the table rows. -3opgl-1@2x.png) For example, to filter the values in a data table as shown above, begin by creating a table with the original data. ```swift let data: [String: MLDataValueConvertible] = [ "Title": ["Alice in Wonderland", "Hamlet", "Treasure Island", "Peter Pan"], "Genre": ["Fantasy", "Drama", "Adventure", "Fantasy"] ] let table = try? MLDataTable(dictionary: data) else { fatalError("Invalid dictionary data") } ``` After you create the table, use column arithmetic operators or the [`map(_:)`](/documentation/CreateML/MLDataTable/map(_:)-92wrj) method to build a row mask. The subscript uses the Boolean values in the row mask to determine whether to keep a row. ```swift // Retrieve the "Genre" column from the table. guard let genreColumn = table["Genre", String.self] else { fatalError("Missing or invalid 'genre' column in table.") } // Create a new column of Booleans by comparing all of the values // in `Genre` with `Fantasy` using the // `!=(MLDataColumn, String) -> MLDataColumn` operator. let noFantasyMask = genreColumn != "Fantasy" ``` Use `subscript(mask: MLDataColumn)` with the Boolean column–row mask to create a filtered table. ```swift let noFantasyTable = table[noFantasyMask] ``` --- 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)