# subscript(_:) Creates a subset of the column by masking its elements with a data column of Booleans. ``` subscript(mask: MLDataColumn) -> MLUntypedColumn { get } ``` ## Parameters `mask` A Boolean column indicating whether elements should be kept (`true`) or removed (`false`) in the derived column. ## Return Value A new 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)