DataOperationsCatalog.CreateEnumerable<TRow> Metoda

Definice

Obor názvů:

Microsoft.ML

Sestavení:

Microsoft.ML.Data.dll

Balíček:

Microsoft.ML v5.0.0-preview.1.25125.4

Zdroj:

DataOperationsCatalog.cs

Převeďte ho IDataView na silné typy IEnumerable<T>.

public System.Collections.Generic.IEnumerable<TRow> CreateEnumerable<TRow>(Microsoft.ML.IDataView data, bool reuseRowObject, bool ignoreMissingColumns = false, Microsoft.ML.Data.SchemaDefinition schemaDefinition = default) where TRow : class, new();

member this.CreateEnumerable : Microsoft.ML.IDataView * bool * bool * Microsoft.ML.Data.SchemaDefinition -> seq<'Row (requires 'Row : null and 'Row : (new : unit -> 'Row))> (requires 'Row : null and 'Row : (new : unit -> 'Row))

Public Function CreateEnumerable(Of TRow As {Class, New}) (data As IDataView, reuseRowObject As Boolean, Optional ignoreMissingColumns As Boolean = false, Optional schemaDefinition As SchemaDefinition = Nothing) As IEnumerable(Of TRow)

Parametry typu

TRow

Typ položky definované uživatelem.

Parametry

data

IDataView

Podkladové zobrazení dat.

reuseRowObject

Boolean

Určuje, jestli chcete vrátit stejný objekt na každém řádku, nebo přidělit nový objekt na jeden řádek.

ignoreMissingColumns

Boolean

Zda se má případ ignorovat, pokud požadovaný sloupec není v zobrazení dat.

schemaDefinition

SchemaDefinition

Volitelná definice schématu poskytovaná uživatelem Pokud není k dispozici, schéma je odvozeno z definice T.

Návraty

IEnumerable<TRow>

To IEnumerable<T> , které obsahuje data v data. Je možné ho vytvořit vícekrát.

Příklady

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

namespace Samples.Dynamic
{
    public static class DataViewEnumerable
    {
        // A simple case of creating IDataView from
        //IEnumerable.
        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();

            // Get a small dataset as an IEnumerable.
            IEnumerable<SampleTemperatureData> enumerableOfData =
                GetSampleTemperatureData(5);

            // Load dataset into an IDataView. 
            IDataView data = mlContext.Data.LoadFromEnumerable(enumerableOfData);

            // We can now examine the records in the IDataView. We first create an
            // enumerable of rows in the IDataView.
            var rowEnumerable = mlContext.Data
                .CreateEnumerable<SampleTemperatureData>(data,
                reuseRowObject: true);

            // SampleTemperatureDataWithLatitude has the definition of a Latitude
            // column of type float. We can use the parameter ignoreMissingColumns
            // to true to ignore any missing columns in the IDataView. The produced
            // enumerable will have the Latitude field set to the default for the
            // data type, in this case 0. 
            var rowEnumerableIgnoreMissing = mlContext.Data
                .CreateEnumerable<SampleTemperatureDataWithLatitude>(data,
                reuseRowObject: true, ignoreMissingColumns: true);

            Console.WriteLine($"Date\tTemperature");
            foreach (var row in rowEnumerable)
                Console.WriteLine(
                    $"{row.Date.ToString("d")}\t{row.Temperature}");

            // Expected output:
            //  Date    Temperature
            //  1/2/2012        36
            //  1/3/2012        36
            //  1/4/2012        34
            //  1/5/2012        35
            //  1/6/2012        35

            Console.WriteLine($"Date\tTemperature\tLatitude");
            foreach (var row in rowEnumerableIgnoreMissing)
                Console.WriteLine($"{row.Date.ToString("d")}\t{row.Temperature}"
                    + $"\t{row.Latitude}");

            // Expected output:
            //  Date    Temperature     Latitude
            //  1/2/2012        36      0
            //  1/3/2012        36      0
            //  1/4/2012        34      0
            //  1/5/2012        35      0
            //  1/6/2012        35      0
        }

        private class SampleTemperatureData
        {
            public DateTime Date { get; set; }
            public float Temperature { get; set; }
        }

        private class SampleTemperatureDataWithLatitude
        {
            public float Latitude { get; set; }
            public DateTime Date { get; set; }
            public float Temperature { get; set; }
        }

        /// <summary>
        /// Get a fake temperature dataset.
        /// </summary>
        /// <param name="exampleCount">The number of examples to return.</param>
        /// <returns>An enumerable of <see cref="SampleTemperatureData"/>.</returns>
        private static IEnumerable<SampleTemperatureData> GetSampleTemperatureData(
            int exampleCount)

        {
            var rng = new Random(1234321);
            var date = new DateTime(2012, 1, 1);
            float temperature = 39.0f;

            for (int i = 0; i < exampleCount; i++)
            {
                date = date.AddDays(1);
                temperature += rng.Next(-5, 5);
                yield return new SampleTemperatureData
                {
                    Date = date,
                    Temperature =
                    temperature
                };

            }
        }
    }
}