TextCatalog.ProduceNgrams Método

Definición

Espacio de nombres:

Microsoft.ML

Ensamblado:

Microsoft.ML.Transforms.dll

Paquete:

Microsoft.ML v2.0.0

Crea un objeto NgramExtractingEstimator que genera un vector de recuentos de n-gramas (secuencias de palabras consecutivas) encontrados en el texto de entrada.

public static Microsoft.ML.Transforms.Text.NgramExtractingEstimator ProduceNgrams (this Microsoft.ML.TransformsCatalog.TextTransforms catalog, string outputColumnName, string inputColumnName = default, int ngramLength = 2, int skipLength = 0, bool useAllLengths = true, int maximumNgramsCount = 10000000, Microsoft.ML.Transforms.Text.NgramExtractingEstimator.WeightingCriteria weighting = Microsoft.ML.Transforms.Text.NgramExtractingEstimator+WeightingCriteria.Tf);

static member ProduceNgrams : Microsoft.ML.TransformsCatalog.TextTransforms * string * string * int * int * bool * int * Microsoft.ML.Transforms.Text.NgramExtractingEstimator.WeightingCriteria -> Microsoft.ML.Transforms.Text.NgramExtractingEstimator

<Extension()>
Public Function ProduceNgrams (catalog As TransformsCatalog.TextTransforms, outputColumnName As String, Optional inputColumnName As String = Nothing, Optional ngramLength As Integer = 2, Optional skipLength As Integer = 0, Optional useAllLengths As Boolean = true, Optional maximumNgramsCount As Integer = 10000000, Optional weighting As NgramExtractingEstimator.WeightingCriteria = Microsoft.ML.Transforms.Text.NgramExtractingEstimator+WeightingCriteria.Tf) As NgramExtractingEstimator

Parámetros

catalog

TransformsCatalog.TextTransforms

Catálogo de la transformación relacionada con el texto.

outputColumnName

String

Nombre de la columna resultante de la transformación de inputColumnName. El tipo de datos de esta columna será un vector de Single.

inputColumnName

String

Nombre de la columna que se va a transformar. Si se establece nullen , el valor de outputColumnName se usará como origen. Este estimador opera sobre vectores de tipo de datos de claves.

ngramLength

Int32

Longitud del ngrama.

skipLength

Int32

Número de tokens que se omitirán entre cada n-grama. De forma predeterminada, no se omite ningún token.

useAllLengths

Boolean

Si se deben incluir todas las longitudes de n-gramas hasta ngramLength o solo ngramLength.

maximumNgramsCount

Int32

Número máximo de n-gramas que se van a almacenar en el diccionario.

weighting

NgramExtractingEstimator.WeightingCriteria

Medida estadística utilizada para evaluar lo importante que es una palabra o n-grama para un documento en un corpus. Cuando maximumNgramsCount es menor que el número total de n-gramas encontrados, esta medida se usa para determinar qué n-gramas mantener.

Devoluciones

NgramExtractingEstimator

Ejemplos

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

namespace Samples.Dynamic
{
    public static class ProduceNgrams
    {
        public static void Example()
        {
            // Create a new ML context, for ML.NET operations. It can be used for
            // exception tracking and logging, as well as the source of randomness.
            var mlContext = new MLContext();

            // Create a small dataset as an IEnumerable.
            var samples = new List<TextData>()
            {
                new TextData(){ Text = "This is an example to compute n-grams." },
                new TextData(){ Text = "N-gram is a sequence of 'N' consecutive " +
                    "words/tokens." },

                new TextData(){ Text = "ML.NET's ProduceNgrams API produces " +
                    "vector of n-grams." },

                new TextData(){ Text = "Each position in the vector corresponds " +
                    "to a particular n-gram." },

                new TextData(){ Text = "The value at each position corresponds " +
                    "to," },

                new TextData(){ Text = "the number of times n-gram occurred in " +
                    "the data (Tf), or" },

                new TextData(){ Text = "the inverse of the number of documents " +
                    "that contain the n-gram (Idf)," },

                new TextData(){ Text = "or compute both and multiply together " +
                    "(Tf-Idf)." },
            };

            // Convert training data to IDataView.
            var dataview = mlContext.Data.LoadFromEnumerable(samples);

            // A pipeline for converting text into numeric n-gram features.
            // The following call to 'ProduceNgrams' requires the tokenized
            // text /string as input. This is achieved by calling 
            // 'TokenizeIntoWords' first followed by 'ProduceNgrams'. Please note
            // that the length of the output feature vector depends on the n-gram
            // settings.
            var textPipeline = mlContext.Transforms.Text.TokenizeIntoWords("Tokens",
                "Text")
                // 'ProduceNgrams' takes key type as input. Converting the tokens
                // into key type using 'MapValueToKey'.
                .Append(mlContext.Transforms.Conversion.MapValueToKey("Tokens"))
                .Append(mlContext.Transforms.Text.ProduceNgrams("NgramFeatures",
                    "Tokens",
                    ngramLength: 3,
                    useAllLengths: false,
                    weighting: NgramExtractingEstimator.WeightingCriteria.Tf));

            // Fit to data.
            var textTransformer = textPipeline.Fit(dataview);
            var transformedDataView = textTransformer.Transform(dataview);

            // Create the prediction engine to get the n-gram features extracted
            // from the text.
            var predictionEngine = mlContext.Model.CreatePredictionEngine<TextData,
                TransformedTextData>(textTransformer);

            // Convert the text into numeric features.
            var prediction = predictionEngine.Predict(samples[0]);

            // Print the length of the feature vector.
            Console.WriteLine("Number of Features: " + prediction.NgramFeatures
                .Length);

            // Preview of the produced n-grams.
            // Get the slot names from the column's metadata.
            // The slot names for a vector column corresponds to the names
            // associated with each position in the vector.
            VBuffer<ReadOnlyMemory<char>> slotNames = default;
            transformedDataView.Schema["NgramFeatures"].GetSlotNames(ref slotNames);
            var NgramFeaturesColumn = transformedDataView.GetColumn<VBuffer<
                float>>(transformedDataView.Schema["NgramFeatures"]);
            var slots = slotNames.GetValues();
            Console.Write("N-grams: ");
            foreach (var featureRow in NgramFeaturesColumn)
            {
                foreach (var item in featureRow.Items())
                    Console.Write($"{slots[item.Key]}  ");
                Console.WriteLine();
            }

            // Print the first 10 feature values.
            Console.Write("Features: ");
            for (int i = 0; i < 10; i++)
                Console.Write($"{prediction.NgramFeatures[i]:F4}  ");

            //  Expected output:
            //   Number of Features: 52
            //   N-grams:   This|is|an  is|an|example  an|example|to  example|to|compute  to|compute|n-grams.  N-gram|is|a  is|a|sequence  a|sequence|of  sequence|of|'N'  of|'N'|consecutive  ...
            //   Features:     1.0000      1.0000          1.0000           1.0000             1.0000            0.0000      0.0000          0.0000          0.0000          0.0000          ...
        }

        private class TextData
        {
            public string Text { get; set; }
        }

        private class TransformedTextData : TextData
        {
            public float[] NgramFeatures { get; set; }
        }
    }
}