# fitted(toWindows:validateOn:eventHandler:) Fits a model to a sequence of annotated windows with validation. ``` func fitted(toWindows input: some Sequence, MLShapedArray>>, validateOn validation: some Sequence, MLShapedArray>>, eventHandler: EventHandler? = nil) async throws -> LinearTimeSeriesForecaster.Model ``` ## Parameters `input` A sequence of annotated windows. Each window’s shape should be `[inputWindowSize, featureSize]` and each annotation’s shape should be `[forecastWindowSize, annotationSize]`. `validation` A sequence of annotated validation windows. The feature and annotation shapes should be the same as the input parameter. `eventHandler` An event handler. ## Return Value The fitted 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)