# GamBinaryTrainer Class

## Definition

The IEstimator<TTransformer> for training a binary classification model with generalized additive models (GAM).

public sealed class GamBinaryTrainer : Microsoft.ML.Trainers.FastTree.GamTrainerBase<Microsoft.ML.Trainers.FastTree.GamBinaryTrainer.Options,Microsoft.ML.Data.BinaryPredictionTransformer<Microsoft.ML.Calibrators.CalibratedModelParametersBase<Microsoft.ML.Trainers.FastTree.GamBinaryModelParameters,Microsoft.ML.Calibrators.PlattCalibrator>>,Microsoft.ML.Calibrators.CalibratedModelParametersBase<Microsoft.ML.Trainers.FastTree.GamBinaryModelParameters,Microsoft.ML.Calibrators.PlattCalibrator>>
type GamBinaryTrainer = class
inherit GamTrainerBase<GamBinaryTrainer.Options, BinaryPredictionTransformer<CalibratedModelParametersBase<GamBinaryModelParameters, PlattCalibrator>>, CalibratedModelParametersBase<GamBinaryModelParameters, PlattCalibrator>>
Public NotInheritable Class GamBinaryTrainer
Inherits GamTrainerBase(Of GamBinaryTrainer.Options, BinaryPredictionTransformer(Of CalibratedModelParametersBase(Of GamBinaryModelParameters, PlattCalibrator)), CalibratedModelParametersBase(Of GamBinaryModelParameters, PlattCalibrator))
Inheritance

## Remarks

To create this trainer, use Gam or Gam(Options).

### 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

Is normalization required? No
Is caching required? No
Required NuGet in addition to Microsoft.ML Microsoft.ML.FastTree
Exportable to ONNX No

### Training Algorithm Details

Generalized Additive Models, or GAMs, model the data as a set of linearly independent features similar to a linear model. For each feature, the GAM trainer learns a non-linear function, called a "shape function", that computes the response as a function of the feature's value. (In contrast, a linear model fits a linear response (e.g. a line) to each feature.) To score an input, the outputs of all the shape functions are summed and the score is the total value.

This GAM trainer is implemented using shallow gradient boosted trees (e.g. tree stumps) to learn nonparametric shape functions, and is based on the method described in Lou, Caruana, and Gehrke. "Intelligible Models for Classification and Regression." KDD'12, Beijing, China. 2012. After training, an intercept is added to represent the average prediction over the training set, and the shape functions are normalized to represent the deviation from the average prediction. This results in models that are easily interpreted simply by inspecting the intercept and the shape functions. See the sample below for an example of how to train a GAM model and inspect and interpret the results.

## Fields

 The feature column that the trainer expects. (Inherited from TrainerEstimatorBase) The label column that the trainer expects. Can be null, which indicates that label is not used for training. (Inherited from TrainerEstimatorBase) The weight column that the trainer expects. Can be null, which indicates that weight is not used for training. (Inherited from TrainerEstimatorBase)

## Properties

 (Inherited from GamTrainerBase)

## Methods

 Trains and returns a ITransformer. (Inherited from TrainerEstimatorBase) Trains a GamBinaryTrainer using both training and validation data, returns a BinaryPredictionTransformer. (Inherited from TrainerEstimatorBase)

## Extension Methods

 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. 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 are often formed into pipelines with many objects, so we may need to build a chain of estimators via EstimatorChain 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.