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| 1 | +using System; |
| 2 | +using System.Linq; |
| 3 | + |
| 4 | +namespace Microsoft.ML.Samples.Dynamic.Trainers.BinaryClassification.Calibrators |
| 5 | +{ |
| 6 | + public static class FixedPlatt |
| 7 | + { |
| 8 | + public static void Example() |
| 9 | + { |
| 10 | + // Create a new context for ML.NET operations. It can be used for exception tracking and logging, |
| 11 | + // as a catalog of available operations and as the source of randomness. |
| 12 | + // Setting the seed to a fixed number in this example to make outputs deterministic. |
| 13 | + var mlContext = new MLContext(seed: 0); |
| 14 | + |
| 15 | + // Download and featurize the dataset. |
| 16 | + var data = SamplesUtils.DatasetUtils.LoadFeaturizedAdultDataset(mlContext); |
| 17 | + // Leave out 10% of data for testing. |
| 18 | + var trainTestData = mlContext.BinaryClassification.TrainTestSplit(data, testFraction: 0.3); |
| 19 | + |
| 20 | + // Create data training pipeline for non calibrated trainer and train Naive calibrator on top of it. |
| 21 | + var pipeline = mlContext.BinaryClassification.Trainers.AveragedPerceptron(); |
| 22 | + |
| 23 | + // Fit the pipeline, and get a transformer that knows how to score new data. |
| 24 | + var transformer = pipeline.Fit(trainTestData.TrainSet); |
| 25 | + // Fit this pipeline to the training data. |
| 26 | + // Let's score the new data. The score will give us a numerical estimation of the chance that the particular sample |
| 27 | + // bears positive sentiment. This estimate is relative to the numbers obtained. |
| 28 | + var scoredData = transformer.Transform(trainTestData.TestSet); |
| 29 | + var scoredDataPreview = scoredData.Preview(); |
| 30 | + |
| 31 | + PrintRowViewValues(scoredDataPreview); |
| 32 | + // Preview of scoredDataPreview.RowView |
| 33 | + // Score 4.18144 |
| 34 | + // Score -14.10248 |
| 35 | + // Score 2.731951 |
| 36 | + // Score -2.554229 |
| 37 | + // Score 5.36571 |
| 38 | + |
| 39 | + // Let's train a calibrator estimator on this scored dataset. The trained calibrator estimator produces a transformer |
| 40 | + // that can transform the scored data by adding a new column names "Probability". |
| 41 | + var calibratorEstimator = mlContext.BinaryClassification.Calibrators.Platt(slope: -1f, offset: -0.05f); |
| 42 | + var calibratorTransformer = calibratorEstimator.Fit(scoredData); |
| 43 | + |
| 44 | + // Transform the scored data with a calibrator transfomer by adding a new column names "Probability". |
| 45 | + // This column is a calibrated version of the "Score" column, meaning its values are a valid probability value in the [0, 1] interval |
| 46 | + // representing the chance that the respective sample bears positive sentiment. |
| 47 | + var finalData = calibratorTransformer.Transform(scoredData).Preview(); |
| 48 | + PrintRowViewValues(finalData); |
| 49 | + // Score 4.18144 Probability 0.9856767 |
| 50 | + // Score -14.10248 Probability 7.890148E-07 |
| 51 | + // Score 2.731951 Probability 0.9416927 |
| 52 | + // Score -2.554229 Probability 0.07556222 |
| 53 | + // Score 5.36571 Probability 0.9955735 |
| 54 | + } |
| 55 | + |
| 56 | + private static void PrintRowViewValues(Data.DataDebuggerPreview data) |
| 57 | + { |
| 58 | + var firstRows = data.RowView.Take(5); |
| 59 | + |
| 60 | + foreach (Data.DataDebuggerPreview.RowInfo row in firstRows) |
| 61 | + { |
| 62 | + foreach (var kvPair in row.Values) |
| 63 | + { |
| 64 | + if (kvPair.Key.Equals("Score") || kvPair.Key.Equals("Probability")) |
| 65 | + Console.Write($" {kvPair.Key} {kvPair.Value} "); |
| 66 | + } |
| 67 | + Console.WriteLine(); |
| 68 | + } |
| 69 | + } |
| 70 | + } |
| 71 | +} |
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