Compartilhar via


TreeExtensions.Gam Método

Definição

Sobrecargas

Gam(BinaryClassificationCatalog+BinaryClassificationTrainers, String, String, String, Int32, Int32, Double)

Criar GamBinaryTrainer, que prevê um destino usando modelos aditivos generalizados (GAM).

Gam(BinaryClassificationCatalog+BinaryClassificationTrainers, GamBinaryTrainer+Options)

Crie GamBinaryTrainer usando opções avançadas, que prevê um destino usando modelos aditivos generalizados (GAM).

Gam(RegressionCatalog+RegressionTrainers, GamRegressionTrainer+Options)

Crie GamRegressionTrainer usando opções avançadas, que prevê um destino usando modelos aditivos generalizados (GAM).

Gam(RegressionCatalog+RegressionTrainers, String, String, String, Int32, Int32, Double)

Criar GamRegressionTrainer, que prevê um destino usando modelos aditivos generalizados (GAM).

Gam(BinaryClassificationCatalog+BinaryClassificationTrainers, String, String, String, Int32, Int32, Double)

Criar GamBinaryTrainer, que prevê um destino usando modelos aditivos generalizados (GAM).

public static Microsoft.ML.Trainers.FastTree.GamBinaryTrainer Gam (this Microsoft.ML.BinaryClassificationCatalog.BinaryClassificationTrainers catalog, string labelColumnName = "Label", string featureColumnName = "Features", string exampleWeightColumnName = default, int numberOfIterations = 9500, int maximumBinCountPerFeature = 255, double learningRate = 0.002);
static member Gam : Microsoft.ML.BinaryClassificationCatalog.BinaryClassificationTrainers * string * string * string * int * int * double -> Microsoft.ML.Trainers.FastTree.GamBinaryTrainer
<Extension()>
Public Function Gam (catalog As BinaryClassificationCatalog.BinaryClassificationTrainers, Optional labelColumnName As String = "Label", Optional featureColumnName As String = "Features", Optional exampleWeightColumnName As String = Nothing, Optional numberOfIterations As Integer = 9500, Optional maximumBinCountPerFeature As Integer = 255, Optional learningRate As Double = 0.002) As GamBinaryTrainer

Parâmetros

labelColumnName
String

O nome da coluna de rótulo. Os dados da coluna devem ser Boolean.

featureColumnName
String

O nome da coluna de recurso. Os dados da coluna devem ser um vetor de tamanho conhecido de Single.

exampleWeightColumnName
String

O nome da coluna de peso de exemplo (opcional).

numberOfIterations
Int32

O número de iterações a serem usadas no aprendizado dos recursos.

maximumBinCountPerFeature
Int32

O número máximo de compartimentos a serem usados para recursos aproximados.

learningRate
Double

A taxa de aprendizado. Os GAMs funcionam melhor com uma pequena taxa de aprendizado.

Retornos

Exemplos

using System;
using System.Collections.Generic;
using Microsoft.ML;
using Microsoft.ML.Data;

namespace Samples.Dynamic.Trainers.BinaryClassification
{
    public static class Gam
    {
        // This example requires installation of additional NuGet package for 
        // Microsoft.ML.FastTree at
        // https://www.nuget.org/packages/Microsoft.ML.FastTree/
        public static void Example()
        {
            // Create a new context for ML.NET operations. It can be used for
            // exception tracking and logging, as a catalog of available operations
            // and as the source of randomness.
            var mlContext = new MLContext();

            // Create the dataset.
            var samples = GenerateData();

            // Convert the dataset to an IDataView.
            var data = mlContext.Data.LoadFromEnumerable(samples);

            // Create training and validation sets.
            var dataSets = mlContext.Data.TrainTestSplit(data);
            var trainSet = dataSets.TrainSet;
            var validSet = dataSets.TestSet;

            // Create a GAM trainer.
            // Use a small number of bins for this example. The setting below means
            // for each feature, we divide its range into 16 discrete regions for
            // the training process. Note that these regions are not evenly spaced,
            // and that the final model may contain fewer bins, as neighboring bins
            // with identical values will be combined. In general, we recommend
            // using at least the default number of bins, as a small number of bins
            // limits the capacity of the model.
            var trainer = mlContext.BinaryClassification.Trainers
                .Gam(maximumBinCountPerFeature: 16);

            // Fit the model using both of training and validation sets. GAM can use
            // a technique called pruning to tune the model to the validation set
            // after training to improve generalization.
            var model = trainer.Fit(trainSet, validSet);

            // Extract the model parameters.
            var gam = model.Model.SubModel;

            // Now we can inspect the parameters of the Generalized Additive Model
            // to understand the fit and potentially learn about our dataset. First,
            // we will look at the bias; the bias represents the average prediction
            // for the training data.
            Console.WriteLine($"Average prediction: {gam.Bias:0.00}");

            // Now look at the shape functions that the model has learned. Similar
            // to a linear model, we have one response per feature, and they are
            // independent. Unlike a linear model, this response is a generic
            // function instead of a line. Because we have included a bias term,
            // each feature response represents the deviation from the average
            // prediction as a function of the feature value.
            for (int i = 0; i < gam.NumberOfShapeFunctions; i++)
            {
                // Break a line.
                Console.WriteLine();

                // Get the bin upper bounds for the feature.
                var binUpperBounds = gam.GetBinUpperBounds(i);

                // Get the bin effects; these are the function values for each bin.
                var binEffects = gam.GetBinEffects(i);

                // Now, write the function to the console. The function is a set of
                // bins, and the corresponding function values. You can think of
                // GAMs as building a bar-chart or lookup table for each feature.
                Console.WriteLine($"Feature{i}");
                for (int j = 0; j < binUpperBounds.Count; j++)
                    Console.WriteLine(
                        $"x < {binUpperBounds[j]:0.00} => {binEffects[j]:0.000}");

            }

            // Expected output:
            //  Average prediction: 0.82
            //
            //  Feature0
            //  x < -0.44 => 0.286
            //  x < -0.38 => 0.225
            //  x < -0.32 => 0.048
            //  x < -0.26 => -0.110
            //  x < -0.20 => -0.116
            //  x < 0.18 => -0.143
            //  x < 0.25 => -0.115
            //  x < 0.31 => -0.005
            //  x < 0.37 => 0.097
            //  x < 0.44 => 0.263
            //  x < ∞ => 0.284
            //
            //  Feature1
            //  x < 0.00 => -0.350
            //  x < 0.24 => 0.875
            //  x < 0.31 => -0.138
            //  x < ∞ => -0.188

            // Let's consider this output. To score a given example, we look up the
            // first bin where the inequality is satisfied for the feature value.
            // We can look at the whole function to get a sense for how the model
            // responds to the variable on a global level.The model can be seen to
            // reconstruct the parabolic and step-wise function, shifted with
            // respect to the average expected output over the training set.
            // Very few bins are used to model the second feature because the GAM
            // model discards unchanged bins to create smaller models. One last
            // thing to notice is that these feature functions can be noisy. While
            // we know that Feature1 should be symmetric, this is not captured in
            // the model. This is due to noise in the data. Common practice is to
            // use resampling methods to estimate a confidence interval at each bin.
            // This will help to determine if the effect is real or just sampling
            // noise. See for example: Tan, Caruana, Hooker, and Lou.
            // "Distill-and-Compare: Auditing Black-Box Models Using Transparent
            // Model Distillation."
            // <a href='https://arxiv.org/abs/1710.06169'>arXiv:1710.06169</a>."
        }

        private class Data
        {
            public bool Label { get; set; }

            [VectorType(2)]
            public float[] Features { get; set; }
        }

        /// <summary>
        /// Creates a dataset, an IEnumerable of Data objects, for a GAM sample.
        /// Feature1 is a parabola centered around 0, while Feature2 is a simple
        /// piecewise function.
        /// </summary>
        /// <param name="numExamples">The number of examples to generate.</param>
        /// <param name="seed">The seed for the random number generator used to
        /// produce data.</param>
        /// <returns></returns>
        private static IEnumerable<Data> GenerateData(int numExamples = 25000,
            int seed = 1)

        {
            var rng = new Random(seed);
            float centeredFloat() => (float)(rng.NextDouble() - 0.5);
            for (int i = 0; i < numExamples; i++)
            {
                // Generate random, uncoupled features.
                var data = new Data
                {
                    Features = new float[2] { centeredFloat(), centeredFloat() }
                };
                // Compute the label from the shape functions and add noise.
                data.Label = Sigmoid(Parabola(data.Features[0])
                    + SimplePiecewise(data.Features[1]) + centeredFloat()) > 0.5;

                yield return data;
            }
        }

        private static float Parabola(float x) => x * x;

        private static float SimplePiecewise(float x)
        {
            if (x < 0)
                return 0;
            else if (x < 0.25)
                return 1;
            else
                return 0;
        }

        private static double Sigmoid(double x) => 1.0 / (1.0 + Math.Exp(-1 * x));
    }
}

Aplica-se a

Gam(BinaryClassificationCatalog+BinaryClassificationTrainers, GamBinaryTrainer+Options)

Crie GamBinaryTrainer usando opções avançadas, que prevê um destino usando modelos aditivos generalizados (GAM).

public static Microsoft.ML.Trainers.FastTree.GamBinaryTrainer Gam (this Microsoft.ML.BinaryClassificationCatalog.BinaryClassificationTrainers catalog, Microsoft.ML.Trainers.FastTree.GamBinaryTrainer.Options options);
static member Gam : Microsoft.ML.BinaryClassificationCatalog.BinaryClassificationTrainers * Microsoft.ML.Trainers.FastTree.GamBinaryTrainer.Options -> Microsoft.ML.Trainers.FastTree.GamBinaryTrainer
<Extension()>
Public Function Gam (catalog As BinaryClassificationCatalog.BinaryClassificationTrainers, options As GamBinaryTrainer.Options) As GamBinaryTrainer

Parâmetros

options
GamBinaryTrainer.Options

Opções de treinador.

Retornos

Exemplos

using System;
using System.Collections.Generic;
using Microsoft.ML;
using Microsoft.ML.Data;
using Microsoft.ML.Trainers.FastTree;

namespace Samples.Dynamic.Trainers.BinaryClassification
{
    public static class GamWithOptions
    {
        // This example requires installation of additional NuGet package for 
        // Microsoft.ML.FastTree at
        // https://www.nuget.org/packages/Microsoft.ML.FastTree/
        public static void Example()
        {
            // Create a new context for ML.NET operations. It can be used for
            // exception tracking and logging, as a catalog of available operations
            // and as the source of randomness.
            var mlContext = new MLContext();

            // Create the dataset.
            var samples = GenerateData();

            // Convert the dataset to an IDataView.
            var data = mlContext.Data.LoadFromEnumerable(samples);

            // Create training and validation datasets.
            var dataSets = mlContext.Data.TrainTestSplit(data);
            var trainSet = dataSets.TrainSet;
            var validSet = dataSets.TestSet;

            // Create a GAM trainer.
            // Use a small number of bins for this example. The setting below means
            // for each feature, we divide its range into 16 discrete regions for
            // the training process. Note that these regions are not evenly spaced,
            // and that the final model may contain fewer bins, as neighboring bins
            // with identical values will be combined. In general, we recommend
            // using at least the default number of bins, as a small number of bins
            // limits the capacity of the model. Also, set the learning rate to half
            // the default to slow down the gradient descent, and double the number
            // of iterations to compensate.
            var trainer = mlContext.BinaryClassification.Trainers.Gam(
                new GamBinaryTrainer.Options
                {
                    NumberOfIterations = 19000,
                    MaximumBinCountPerFeature = 16,
                    LearningRate = 0.001
                });

            // Fit the model using both of training and validation sets. GAM can use
            // a technique called pruning to tune the model to the validation set
            // after training to improve generalization.
            var model = trainer.Fit(trainSet, validSet);

            // Extract the model parameters.
            var gam = model.Model.SubModel;

            // Now we can inspect the parameters of the Generalized Additive Model
            // to understand the fit and potentially learn about our dataset. First,
            // we will look at the bias; the bias represents the average prediction
            // for the training data.
            Console.WriteLine($"Average prediction: {gam.Bias:0.00}");

            // Now look at the shape functions that the model has learned. Similar
            // to a linear model, we have one response per feature, and they are
            // independent. Unlike a linear model, this response is a generic
            // function instead of a line. Because we have included a bias term,
            // each feature response represents the deviation from the average
            // prediction as a function of the feature value.
            for (int i = 0; i < gam.NumberOfShapeFunctions; i++)
            {
                // Break a line.
                Console.WriteLine();

                // Get the bin upper bounds for the feature.
                var binUpperBounds = gam.GetBinUpperBounds(i);

                // Get the bin effects; these are the function values for each bin.
                var binEffects = gam.GetBinEffects(i);

                // Now, write the function to the console. The function is a set of
                // bins, and the corresponding function values. You can think of
                // GAMs as building a bar-chart or lookup table for each feature.
                Console.WriteLine($"Feature{i}");
                for (int j = 0; j < binUpperBounds.Count; j++)
                    Console.WriteLine(
                        $"x < {binUpperBounds[j]:0.00} => {binEffects[j]:0.000}");
            }

            // Expected output:
            //  Average prediction: 0.82
            //
            //  Feature0
            //  x < -0.44 => 0.286
            //  x < -0.38 => 0.225
            //  x < -0.32 => 0.048
            //  x < -0.26 => -0.110
            //  x < -0.20 => -0.116
            //  x < 0.18 => -0.143
            //  x < 0.25 => -0.115
            //  x < 0.31 => -0.005
            //  x < 0.37 => 0.097
            //  x < 0.44 => 0.263
            //  x < ∞ => 0.284
            //
            //  Feature1
            //  x < 0.00 => -0.350
            //  x < 0.24 => 0.875
            //  x < 0.31 => -0.138
            //  x < ∞ => -0.188

            // Let's consider this output. To score a given example, we look up the
            // first bin where the inequality is satisfied for the feature value.
            // We can look at the whole function to get a sense for how the model
            // responds to the variable on a global level. The model can be seen to
            // reconstruct the parabolic and step-wise function, shifted with
            // respect to the average expected output over the training set. Very
            // few bins are used to model the second feature because the GAM model
            // discards unchanged bins to create smaller models.One last thing to
            // notice is that these feature functions can be noisy. While we know
            // that Feature1 should be symmetric, this is not captured in the model.
            // This is due to noise in the data. Common practice is to use
            // resampling methods to estimate a confidence interval at each bin.
            // This will help to determine if the effect is real or just sampling
            // noise. See for example: Tan, Caruana, Hooker, and Lou.
            // "Distill-and-Compare: Auditing Black-Box Models Using Transparent
            // Model Distillation."
            // <a href='https://arxiv.org/abs/1710.06169'>arXiv:1710.06169</a>."
        }

        private class Data
        {
            public bool Label { get; set; }

            [VectorType(2)]
            public float[] Features { get; set; }
        }

        /// <summary>
        /// Creates a dataset, an IEnumerable of Data objects, for a GAM sample.
        /// Feature1 is a parabola centered around 0, while Feature2 is a simple
        /// piecewise function.
        /// </summary>
        /// <param name="numExamples">The number of examples to generate.</param>
        /// <param name="seed">The seed for the random number generator used to
        /// produce data.</param>
        /// <returns></returns>
        private static IEnumerable<Data> GenerateData(int numExamples = 25000,
            int seed = 1)

        {
            var rng = new Random(seed);
            float centeredFloat() => (float)(rng.NextDouble() - 0.5);
            for (int i = 0; i < numExamples; i++)
            {
                // Generate random, uncoupled features.
                var data = new Data
                {
                    Features = new float[2] { centeredFloat(), centeredFloat() }
                };
                // Compute the label from the shape functions and add noise.
                data.Label = Sigmoid(Parabola(data.Features[0]) +
                    SimplePiecewise(data.Features[1]) + centeredFloat()) > 0.5;

                yield return data;
            }
        }

        private static float Parabola(float x) => x * x;

        private static float SimplePiecewise(float x)
        {
            if (x < 0)
                return 0;
            else if (x < 0.25)
                return 1;
            else
                return 0;
        }

        private static double Sigmoid(double x) => 1.0 / (1.0 + Math.Exp(-1 * x));
    }
}

Aplica-se a

Gam(RegressionCatalog+RegressionTrainers, GamRegressionTrainer+Options)

Crie GamRegressionTrainer usando opções avançadas, que prevê um destino usando modelos aditivos generalizados (GAM).

public static Microsoft.ML.Trainers.FastTree.GamRegressionTrainer Gam (this Microsoft.ML.RegressionCatalog.RegressionTrainers catalog, Microsoft.ML.Trainers.FastTree.GamRegressionTrainer.Options options);
static member Gam : Microsoft.ML.RegressionCatalog.RegressionTrainers * Microsoft.ML.Trainers.FastTree.GamRegressionTrainer.Options -> Microsoft.ML.Trainers.FastTree.GamRegressionTrainer
<Extension()>
Public Function Gam (catalog As RegressionCatalog.RegressionTrainers, options As GamRegressionTrainer.Options) As GamRegressionTrainer

Parâmetros

options
GamRegressionTrainer.Options

Opções de treinador.

Retornos

Exemplos

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.ML;
using Microsoft.ML.Data;
using Microsoft.ML.Trainers.FastTree;

namespace Samples.Dynamic.Trainers.Regression
{
    public static class GamWithOptions
    {
        // This example requires installation of additional NuGet
        // package for Microsoft.ML.FastTree found at
        // https://www.nuget.org/packages/Microsoft.ML.FastTree/
        public static void Example()
        {
            // Create a new context for ML.NET operations. It can be used for
            // exception tracking and logging, as a catalog of available operations
            // and as the source of randomness. Setting the seed to a fixed number
            // in this example to make outputs deterministic.
            var mlContext = new MLContext(seed: 0);

            // Create a list of training data points.
            var dataPoints = GenerateRandomDataPoints(1000);

            // Convert the list of data points to an IDataView object, which is
            // consumable by ML.NET API.
            var trainingData = mlContext.Data.LoadFromEnumerable(dataPoints);

            // Define trainer options.
            var options = new GamRegressionTrainer.Options
            {
                LabelColumnName = nameof(DataPoint.Label),
                FeatureColumnName = nameof(DataPoint.Features),
                // The entropy (regularization) coefficient.
                EntropyCoefficient = 0.3,
                // Reduce the number of iterations to 50.
                NumberOfIterations = 50
            };

            // Define the trainer.
            var pipeline =
                mlContext.Regression.Trainers.Gam(options);

            // Train the model.
            var model = pipeline.Fit(trainingData);

            // Create testing data. Use different random seed to make it different
            // from training data.
            var testData = mlContext.Data.LoadFromEnumerable(
                GenerateRandomDataPoints(5, seed: 123));

            // Run the model on test data set.
            var transformedTestData = model.Transform(testData);

            // Convert IDataView object to a list.
            var predictions = mlContext.Data.CreateEnumerable<Prediction>(
                transformedTestData, reuseRowObject: false).ToList();

            // Look at 5 predictions for the Label, side by side with the actual
            // Label for comparison.
            foreach (var p in predictions)
                Console.WriteLine($"Label: {p.Label:F3}, Prediction: {p.Score:F3}");

            // Expected output:
            //   Label: 0.985, Prediction: 0.841
            //   Label: 0.155, Prediction: 0.187
            //   Label: 0.515, Prediction: 0.496
            //   Label: 0.566, Prediction: 0.467
            //   Label: 0.096, Prediction: 0.144

            // Evaluate the overall metrics
            var metrics = mlContext.Regression.Evaluate(transformedTestData);
            PrintMetrics(metrics);

            // Expected output:
            //   Mean Absolute Error: 0.04
            //   Mean Squared Error: 0.01
            //   Root Mean Squared Error: 0.05
            //   RSquared: 0.98 (closer to 1 is better. The worst case is 0)
        }

        private static IEnumerable<DataPoint> GenerateRandomDataPoints(int count,
            int seed = 0)
        {
            var random = new Random(seed);
            for (int i = 0; i < count; i++)
            {
                float label = (float)random.NextDouble();
                yield return new DataPoint
                {
                    Label = label,
                    // Create random features that are correlated with the label.
                    Features = Enumerable.Repeat(label, 50).Select(
                        x => x + (float)random.NextDouble()).ToArray()
                };
            }
        }

        // Example with label and 50 feature values. A data set is a collection of
        // such examples.
        private class DataPoint
        {
            public float Label { get; set; }
            [VectorType(50)]
            public float[] Features { get; set; }
        }

        // Class used to capture predictions.
        private class Prediction
        {
            // Original label.
            public float Label { get; set; }
            // Predicted score from the trainer.
            public float Score { get; set; }
        }

        // Print some evaluation metrics to regression problems.
        private static void PrintMetrics(RegressionMetrics metrics)
        {
            Console.WriteLine("Mean Absolute Error: " + metrics.MeanAbsoluteError);
            Console.WriteLine("Mean Squared Error: " + metrics.MeanSquaredError);
            Console.WriteLine(
                "Root Mean Squared Error: " + metrics.RootMeanSquaredError);

            Console.WriteLine("RSquared: " + metrics.RSquared);
        }
    }
}

Aplica-se a

Gam(RegressionCatalog+RegressionTrainers, String, String, String, Int32, Int32, Double)

Criar GamRegressionTrainer, que prevê um destino usando modelos aditivos generalizados (GAM).

public static Microsoft.ML.Trainers.FastTree.GamRegressionTrainer Gam (this Microsoft.ML.RegressionCatalog.RegressionTrainers catalog, string labelColumnName = "Label", string featureColumnName = "Features", string exampleWeightColumnName = default, int numberOfIterations = 9500, int maximumBinCountPerFeature = 255, double learningRate = 0.002);
static member Gam : Microsoft.ML.RegressionCatalog.RegressionTrainers * string * string * string * int * int * double -> Microsoft.ML.Trainers.FastTree.GamRegressionTrainer
<Extension()>
Public Function Gam (catalog As RegressionCatalog.RegressionTrainers, Optional labelColumnName As String = "Label", Optional featureColumnName As String = "Features", Optional exampleWeightColumnName As String = Nothing, Optional numberOfIterations As Integer = 9500, Optional maximumBinCountPerFeature As Integer = 255, Optional learningRate As Double = 0.002) As GamRegressionTrainer

Parâmetros

labelColumnName
String

O nome da coluna de rótulo. Os dados da coluna devem ser Single.

featureColumnName
String

O nome da coluna de recurso. Os dados da coluna devem ser um vetor de tamanho conhecido de Single.

exampleWeightColumnName
String

O nome da coluna de peso de exemplo (opcional).

numberOfIterations
Int32

O número de iterações a serem usadas no aprendizado dos recursos.

maximumBinCountPerFeature
Int32

O número máximo de compartimentos a serem usados para recursos aproximados.

learningRate
Double

A taxa de aprendizado. Os GAMs funcionam melhor com uma pequena taxa de aprendizado.

Retornos

Exemplos

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.ML;
using Microsoft.ML.Data;

namespace Samples.Dynamic.Trainers.Regression
{
    public static class Gam
    {
        // This example requires installation of additional NuGet
        // package for Microsoft.ML.FastTree found at
        // https://www.nuget.org/packages/Microsoft.ML.FastTree/
        public static void Example()
        {
            // Create a new context for ML.NET operations. It can be used for
            // exception tracking and logging, as a catalog of available operations
            // and as the source of randomness. Setting the seed to a fixed number
            // in this example to make outputs deterministic.
            var mlContext = new MLContext(seed: 0);

            // Create a list of training data points.
            var dataPoints = GenerateRandomDataPoints(1000);

            // Convert the list of data points to an IDataView object, which is
            // consumable by ML.NET API.
            var trainingData = mlContext.Data.LoadFromEnumerable(dataPoints);

            // Define the trainer.
            var pipeline = mlContext.Regression.Trainers.Gam(
                labelColumnName: nameof(DataPoint.Label),
                featureColumnName: nameof(DataPoint.Features));

            // Train the model.
            var model = pipeline.Fit(trainingData);

            // Create testing data. Use different random seed to make it different
            // from training data.
            var testData = mlContext.Data.LoadFromEnumerable(
                GenerateRandomDataPoints(5, seed: 123));

            // Run the model on test data set.
            var transformedTestData = model.Transform(testData);

            // Convert IDataView object to a list.
            var predictions = mlContext.Data.CreateEnumerable<Prediction>(
                transformedTestData, reuseRowObject: false).ToList();

            // Look at 5 predictions for the Label, side by side with the actual
            // Label for comparison.
            foreach (var p in predictions)
                Console.WriteLine($"Label: {p.Label:F3}, Prediction: {p.Score:F3}");

            // Expected output:
            //   Label: 0.985, Prediction: 0.948
            //   Label: 0.155, Prediction: 0.089
            //   Label: 0.515, Prediction: 0.463
            //   Label: 0.566, Prediction: 0.509
            //   Label: 0.096, Prediction: 0.106

            // Evaluate the overall metrics
            var metrics = mlContext.Regression.Evaluate(transformedTestData);
            PrintMetrics(metrics);

            // Expected output:
            //   Mean Absolute Error: 0.03
            //   Mean Squared Error: 0.00
            //   Root Mean Squared Error: 0.03
            //   RSquared: 0.99 (closer to 1 is better. The worst case is 0)
        }

        private static IEnumerable<DataPoint> GenerateRandomDataPoints(int count,
            int seed = 0)
        {
            var random = new Random(seed);
            for (int i = 0; i < count; i++)
            {
                float label = (float)random.NextDouble();
                yield return new DataPoint
                {
                    Label = label,
                    // Create random features that are correlated with the label.
                    Features = Enumerable.Repeat(label, 50).Select(
                        x => x + (float)random.NextDouble()).ToArray()
                };
            }
        }

        // Example with label and 50 feature values. A data set is a collection of
        // such examples.
        private class DataPoint
        {
            public float Label { get; set; }
            [VectorType(50)]
            public float[] Features { get; set; }
        }

        // Class used to capture predictions.
        private class Prediction
        {
            // Original label.
            public float Label { get; set; }
            // Predicted score from the trainer.
            public float Score { get; set; }
        }

        // Print some evaluation metrics to regression problems.
        private static void PrintMetrics(RegressionMetrics metrics)
        {
            Console.WriteLine("Mean Absolute Error: " + metrics.MeanAbsoluteError);
            Console.WriteLine("Mean Squared Error: " + metrics.MeanSquaredError);
            Console.WriteLine(
                "Root Mean Squared Error: " + metrics.RootMeanSquaredError);

            Console.WriteLine("RSquared: " + metrics.RSquared);
        }
    }
}

Aplica-se a