PriorTrainer Class


The IEstimator<TTransformer> for predicting a target using a binary classification model.

public sealed class PriorTrainer : Microsoft.ML.IEstimator<Microsoft.ML.Data.BinaryPredictionTransformer<Microsoft.ML.Trainers.PriorModelParameters>>, Microsoft.ML.Trainers.ITrainerEstimator<Microsoft.ML.Data.BinaryPredictionTransformer<Microsoft.ML.Trainers.PriorModelParameters>,Microsoft.ML.Trainers.PriorModelParameters>
type PriorTrainer = class
    interface ITrainerEstimator<BinaryPredictionTransformer<PriorModelParameters>, PriorModelParameters>
    interface IEstimator<BinaryPredictionTransformer<PriorModelParameters>>
Public NotInheritable Class PriorTrainer
Implements IEstimator(Of BinaryPredictionTransformer(Of PriorModelParameters)), ITrainerEstimator(Of BinaryPredictionTransformer(Of PriorModelParameters), PriorModelParameters)


To create this trainer, use Prior

Input and Output Columns

The input label column data must be Boolean. The input features column data must be a known-sized vector of Single.

This trainer outputs the following columns:

Output Column Name Column Type Description
Score Single The unbounded score that was calculated by the model.
PredictedLabel Boolean The predicted label, based on the sign of the score. A negative score maps to false and a positive score maps to true.
Probability Single The probability calculated by calibrating the score of having true as the label. Probability value is in range [0, 1].

Trainer Characteristics

Machine learning task Binary classification
Is normalization required? No
Is caching required? No
Required NuGet in addition to Microsoft.ML None
Exportable to ONNX Yes

Training Algorithm Details

Learns the prior distribution for 0/1 class labels and outputs that.

Check the See Also section for links to usage examples.



Auxiliary information about the trainer in terms of its capabilities and requirements.



Trains and returns a BinaryPredictionTransformer<TModel>.


Returns the SchemaShape of the schema which will be produced by the transformer. Used for schema propagation and verification in a pipeline.

Extension Methods

AppendCacheCheckpoint<TTrans>(IEstimator<TTrans>, IHostEnvironment)

Append a 'caching checkpoint' to the estimator chain. This will ensure that the downstream estimators will be trained against cached data. It is helpful to have a caching checkpoint before trainers that take multiple data passes.

WithOnFitDelegate<TTransformer>(IEstimator<TTransformer>, Action<TTransformer>)

Given an estimator, return a wrapping object that will call a delegate once Fit(IDataView) is called. It is often important for an estimator to return information about what was fit, which is why the Fit(IDataView) method returns a specifically typed object, rather than just a general ITransformer. However, at the same time, IEstimator<TTransformer> are often formed into pipelines with many objects, so we may need to build a chain of estimators via EstimatorChain<TLastTransformer> where the estimator for which we want to get the transformer is buried somewhere in this chain. For that scenario, we can through this method attach a delegate that will be called once fit is called.

Applies to

See also