StandardTrainersCatalog.PairwiseCoupling<TModel> Metode
Definisi
Penting
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Buat PairwiseCouplingTrainer, yang memprediksi target multikelas menggunakan strategi coupling pairwise dengan estimator klasifikasi biner yang ditentukan oleh binaryEstimator
.
public static Microsoft.ML.Trainers.PairwiseCouplingTrainer PairwiseCoupling<TModel> (this Microsoft.ML.MulticlassClassificationCatalog.MulticlassClassificationTrainers catalog, Microsoft.ML.Trainers.ITrainerEstimator<Microsoft.ML.ISingleFeaturePredictionTransformer<TModel>,TModel> binaryEstimator, string labelColumnName = "Label", bool imputeMissingLabelsAsNegative = false, Microsoft.ML.IEstimator<Microsoft.ML.ISingleFeaturePredictionTransformer<Microsoft.ML.Calibrators.ICalibrator>> calibrator = default, int maximumCalibrationExampleCount = 1000000000) where TModel : class;
static member PairwiseCoupling : Microsoft.ML.MulticlassClassificationCatalog.MulticlassClassificationTrainers * Microsoft.ML.Trainers.ITrainerEstimator<Microsoft.ML.ISingleFeaturePredictionTransformer<'Model>, 'Model (requires 'Model : null)> * string * bool * Microsoft.ML.IEstimator<Microsoft.ML.ISingleFeaturePredictionTransformer<Microsoft.ML.Calibrators.ICalibrator>> * int -> Microsoft.ML.Trainers.PairwiseCouplingTrainer (requires 'Model : null)
<Extension()>
Public Function PairwiseCoupling(Of TModel As Class) (catalog As MulticlassClassificationCatalog.MulticlassClassificationTrainers, binaryEstimator As ITrainerEstimator(Of ISingleFeaturePredictionTransformer(Of TModel), TModel), Optional labelColumnName As String = "Label", Optional imputeMissingLabelsAsNegative As Boolean = false, Optional calibrator As IEstimator(Of ISingleFeaturePredictionTransformer(Of ICalibrator)) = Nothing, Optional maximumCalibrationExampleCount As Integer = 1000000000) As PairwiseCouplingTrainer
Jenis parameter
- TModel
Jenis model. Parameter jenis ini biasanya akan disimpulkan secara otomatis dari binaryEstimator
.
Parameter
Objek pelatih katalog klasifikasi multikelas.
- binaryEstimator
- ITrainerEstimator<ISingleFeaturePredictionTransformer<TModel>,TModel>
Instans biner ITrainerEstimator<TTransformer,TModel> yang digunakan sebagai pelatih dasar.
- labelColumnName
- String
Nama kolom label.
- imputeMissingLabelsAsNegative
- Boolean
Apakah memperlakukan label yang hilang sebagai memiliki label negatif, alih-alih membuatnya hilang.
- calibrator
- IEstimator<ISingleFeaturePredictionTransformer<ICalibrator>>
Kalibratornya. Jika kalibrator tidak disediakan secara eksplisit, akan default ke Microsoft.ML.Calibrators.PlattCalibratorTrainer
- maximumCalibrationExampleCount
- Int32
Jumlah instans untuk melatih kalibrasi.
Mengembalikan
Contoh
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.ML;
using Microsoft.ML.Data;
namespace Samples.Dynamic.Trainers.MulticlassClassification
{
public static class PairwiseCoupling
{
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 =
// Convert the string labels into key types.
mlContext.Transforms.Conversion.MapValueToKey("Label")
// Apply PairwiseCoupling multiclass meta trainer on top of
// binary trainer.
.Append(mlContext.MulticlassClassification.Trainers
.PairwiseCoupling(
mlContext.BinaryClassification.Trainers.SdcaLogisticRegression()));
// 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(500, 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
foreach (var p in predictions.Take(5))
Console.WriteLine($"Label: {p.Label}, " +
$"Prediction: {p.PredictedLabel}");
// Expected output:
// Label: 1, Prediction: 1
// Label: 2, Prediction: 2
// Label: 3, Prediction: 2
// Label: 2, Prediction: 2
// Label: 3, Prediction: 2
// Evaluate the overall metrics
var metrics = mlContext.MulticlassClassification
.Evaluate(transformedTestData);
PrintMetrics(metrics);
// Expected output:
// Micro Accuracy: 0.90
// Macro Accuracy: 0.90
// Log Loss: 0.36
// Log Loss Reduction: 0.67
// Confusion table
// ||========================
// PREDICTED || 0 | 1 | 2 | Recall
// TRUTH ||========================
// 0 || 150 | 0 | 10 | 0.9375
// 1 || 0 | 166 | 11 | 0.9379
// 2 || 15 | 15 | 133 | 0.8160
// ||========================
// Precision ||0.9091 |0.9171 |0.8636 |
}
// Generates random uniform doubles in [-0.5, 0.5)
// range with labels 1, 2 or 3.
private static IEnumerable<DataPoint> GenerateRandomDataPoints(int count,
int seed = 0)
{
var random = new Random(seed);
float randomFloat() => (float)(random.NextDouble() - 0.5);
for (int i = 0; i < count; i++)
{
// Generate Labels that are integers 1, 2 or 3
var label = random.Next(1, 4);
yield return new DataPoint
{
Label = (uint)label,
// Create random features that are correlated with the label.
// The feature values are slightly increased by adding a
// constant multiple of label.
Features = Enumerable.Repeat(label, 20)
.Select(x => randomFloat() + label * 0.2f).ToArray()
};
}
}
// Example with label and 20 feature values. A data set is a collection of
// such examples.
private class DataPoint
{
public uint Label { get; set; }
[VectorType(20)]
public float[] Features { get; set; }
}
// Class used to capture predictions.
private class Prediction
{
// Original label.
public uint Label { get; set; }
// Predicted label from the trainer.
public uint PredictedLabel { get; set; }
}
// Pretty-print MulticlassClassificationMetrics objects.
public static void PrintMetrics(MulticlassClassificationMetrics metrics)
{
Console.WriteLine($"Micro Accuracy: {metrics.MicroAccuracy:F2}");
Console.WriteLine($"Macro Accuracy: {metrics.MacroAccuracy:F2}");
Console.WriteLine($"Log Loss: {metrics.LogLoss:F2}");
Console.WriteLine(
$"Log Loss Reduction: {metrics.LogLossReduction:F2}\n");
Console.WriteLine(metrics.ConfusionMatrix.GetFormattedConfusionTable());
}
}
}
Keterangan
Dalam strategi pairwise coupling (PKPD), algoritma klasifikasi biner digunakan untuk melatih satu pengklasifikasi untuk setiap pasangan kelas. Prediksi kemudian dilakukan dengan menjalankan pengklasifikasi biner ini, dan menghitung skor untuk setiap kelas dengan menghitung berapa banyak pengklasifikasi biner yang memprediksinya. Prediksinya adalah kelas dengan skor tertinggi.