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# train(trainingData:featureColumns:labelColumn:recordingFileColumn:parameters:sessionParameters:)

Begins an asynchronous activity classifier training session with a
training dataset represented by a data source.

```
static func train(trainingData: MLActivityClassifier.DataSource, featureColumns: [String], labelColumn: String, recordingFileColumn: String, parameters: MLActivityClassifier.ModelParameters = ModelParameters(validationData: nil), sessionParameters: MLTrainingSessionParameters = _defaultSessionParameters) throws -> MLJob<MLActivityClassifier>
```

## Parameters

`trainingData`

An [`MLActivityClassifier.DataSource`](/documentation/CreateML/MLActivityClassifier/DataSource) instance.

`featureColumns`

The names of the columns in an annotation file that contain sensor data.

`labelColumn`

The name of the column in an annotation file that contains the activity labels if `trainingData` uses
[`MLActivityClassifier.DataSource.directoryWithDataAndAnnotation(at:annotationFileName:timeStampColumn:labelStartTimeColumn:labelEndTimeColumn:)`](/documentation/CreateML/MLActivityClassifier/DataSource/directoryWithDataAndAnnotation(at:annotationFileName:timeStampColumn:labelStartTimeColumn:labelEndTimeColumn:)).

    The initializer ignores this parameter if     `trainingData`     uses
[`MLActivityClassifier.DataSource.labeledDirectories(at:)`](/documentation/CreateML/MLActivityClassifier/DataSource/labeledDirectories(at:))    .

`recordingFileColumn`

The name of the column in an annotation file that contains the data filenames if
`trainingData` uses
[`MLActivityClassifier.DataSource.directoryWithDataAndAnnotation(at:annotationFileName:timeStampColumn:labelStartTimeColumn:labelEndTimeColumn:)`](/documentation/CreateML/MLActivityClassifier/DataSource/directoryWithDataAndAnnotation(at:annotationFileName:timeStampColumn:labelStartTimeColumn:labelEndTimeColumn:)).

    The initializer ignores this parameter if     `trainingData`     uses
[`MLActivityClassifier.DataSource.labeledDirectories(at:)`](/documentation/CreateML/MLActivityClassifier/DataSource/labeledDirectories(at:))    .

`parameters`

An [`MLActivityClassifier.ModelParameters`](/documentation/CreateML/MLActivityClassifier/ModelParameters-swift.struct) instance you use to configure the
model for the training session.

`sessionParameters`

An [`MLTrainingSessionParameters`](/documentation/CreateML/MLTrainingSessionParameters) instance you use to configure the training session.

## Return Value

An [`MLJob`](/documentation/CreateML/MLJob) that represents the activity classifier training
session.

---

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