# Estimator An estimator that creates a transformer by fitting to a data set. ``` protocol Estimator ``` ## Topics ### Getting the properties [`associatedtype Transformer : Transformer`](/documentation/CreateMLComponents/Estimator/Transformer) The transformer type created by this estimator. ### Appending [`func appending(_:)`](/documentation/CreateMLComponents/Estimator/appending(_:)) Composes this estimator with another estimator. ### Encoding and decoding [`func encode(Self.Transformer, to: inout any EstimatorEncoder) throws`](/documentation/CreateMLComponents/Estimator/encode(_:to:)) Encodes a fitted transformer. [`func decode(from: inout any EstimatorDecoder) throws -> Self.Transformer`](/documentation/CreateMLComponents/Estimator/decode(from:)) Decodes a previously fitted transformer. ### Reading and writing [`func read(from: URL) throws -> Self.Transformer`](/documentation/CreateMLComponents/Estimator/read(from:)) Reads the encoded transformer from a file. [`func write(Self.Transformer, to: URL, overwrite: Bool) throws`](/documentation/CreateMLComponents/Estimator/write(_:to:overwrite:)) Writes the encoded transformer to a file. ### Fitting and adapting [`func adaptedAsSupervised(annotationType: Annotation.Type) -> EstimatorToSupervisedAdaptor`](/documentation/CreateMLComponents/Estimator/adaptedAsSupervised(annotationType:)) Exposes this estimator as a supervised estimator. [`func adaptedAsTemporal() -> EstimatorToTemporalAdaptor`](/documentation/CreateMLComponents/Estimator/adaptedAsTemporal()) Exposes this estimator as a temporal estimator. [`func fitted(to: S, eventHandler: EventHandler?) async throws -> Self.Transformer`](/documentation/CreateMLComponents/Estimator/fitted(to:eventHandler:)) Fits a transformer to a sequence of examples. [`func fitted(to: S) async throws -> Self.Transformer`](/documentation/CreateMLComponents/Estimator/fitted(to:)) ## Relationships ### Conforming Types [`OneHotEncoder`](/documentation/CreateMLComponents/OneHotEncoder) [`NumericImputer`](/documentation/CreateMLComponents/NumericImputer) [`CategoricalImputer`](/documentation/CreateMLComponents/CategoricalImputer) [`PreprocessingEstimator`](/documentation/CreateMLComponents/PreprocessingEstimator) [`TransformerToUpdatableEstimatorAdaptor`](/documentation/CreateMLComponents/TransformerToUpdatableEstimatorAdaptor) [`TransformerToEstimatorAdaptor`](/documentation/CreateMLComponents/TransformerToEstimatorAdaptor) [`OrdinalEncoder`](/documentation/CreateMLComponents/OrdinalEncoder) [`NormalizationScaler`](/documentation/CreateMLComponents/NormalizationScaler) [`RobustScaler`](/documentation/CreateMLComponents/RobustScaler) [`PreprocessingUpdatableEstimator`](/documentation/CreateMLComponents/PreprocessingUpdatableEstimator) [`MinMaxScaler`](/documentation/CreateMLComponents/MinMaxScaler) [`StandardScaler`](/documentation/CreateMLComponents/StandardScaler) [`MaxAbsScaler`](/documentation/CreateMLComponents/MaxAbsScaler) ### Inherited By [`UpdatableEstimator`](/documentation/CreateMLComponents/UpdatableEstimator) --- 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)