# CategoricalImputer An estimator that replaces missing values in the categorical input. ``` struct CategoricalImputer where Element : Decodable, Element : Encodable, Element : Hashable ``` ## Topics ### Creating an estimator [`init(CategoricalImputer.Strategy)`](/documentation/CreateMLComponents/CategoricalImputer/init(_:)) Creates an imputer with a strategy. [`init(constant: Element)`](/documentation/CreateMLComponents/CategoricalImputer/init(constant:)) Creates an imputer with a constant value to use when replacing missing values. ### Getting the properties [`var strategy: CategoricalImputer.Strategy`](/documentation/CreateMLComponents/CategoricalImputer/strategy-swift.property) The imputation strategy. ### Fitting [`func fitted(to: S, eventHandler: EventHandler?) -> CategoricalImputer.Transformer`](/documentation/CreateMLComponents/CategoricalImputer/fitted(to:eventHandler:)) Fits a categorical imputer to a sequence of elements. [`protocol Transformer`](/documentation/CreateMLComponents/Transformer) A transformer that takes an input and produces an output. [`enum Strategy`](/documentation/CreateMLComponents/CategoricalImputer/Strategy-swift.enum) An imputation strategy. ## Relationships ### Conforms To [`Estimator`](/documentation/CreateMLComponents/Estimator) [`Escapable`](/documentation/Swift/Escapable) [`Sendable`](/documentation/Swift/Sendable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) [`Copyable`](/documentation/Swift/Copyable) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) --- 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)