# fitted(to:validateOn:eventHandler:) Fits a boosted tree classifier model to a collection of examples. ``` func fitted(to input: DataFrame, validateOn validation: DataFrame? = nil, eventHandler: EventHandler? = nil) async throws -> TreeClassifierModel ``` ## Parameters `input` A data frame of examples. `validation` A data frame of validation examples. `eventHandler` An event handler. This method reports accuracy and loss metrics. ## Return Value The fitted boosted tree classifier model. --- 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)