# mapMissing(_:) Creates a new column, potentially with missing elements, by applying the given thread-safe transform to every element of the column, including missing elements. ``` func mapMissing(_ lazyTransform: @escaping (Element?) -> T?) -> MLDataColumn where T : MLDataValueConvertible ``` ## Parameters `lazyTransform` A thread-safe element transformation function. The implementation of the transform you provide should accept an `Element` of the column and return a transformed value of a type that conforms to [`MLDataValueConvertible`](/documentation/CreateML/MLDataValueConvertible). If the transform returns `nil` for a given element, the corresponding element in the new column will have a missing value. ## 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)