DataOperationsCatalog.SkipRows(IDataView, Int64) Methode

Definition

Namespace:

Microsoft.ML

Assembly:

Microsoft.ML.Data.dll

Paket:

Microsoft.ML v4.0.0-preview.24522.7

Quelle:

DataOperationsCatalog.cs

Überspringen Sie count Zeilen in input.

public Microsoft.ML.IDataView SkipRows(Microsoft.ML.IDataView input, long count);

member this.SkipRows : Microsoft.ML.IDataView * int64 -> Microsoft.ML.IDataView

Public Function SkipRows (input As IDataView, count As Long) As IDataView

Parameter

input

IDataView

Die Eingabedaten.

count

Int64

Anzahl der Zeilen, die übersprungen werden sollen.

Gibt zurück

IDataView

Beispiele

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

namespace Samples.Dynamic
{
    public static class SkipRows
    {
        // Sample class showing how to skip rows in IDataView.
        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.
            var enumerableOfData = GetSampleTemperatureData(10);
            var data = mlContext.Data.LoadFromEnumerable(enumerableOfData);

            // Before we apply a filter, examine all the records in the dataset.
            Console.WriteLine($"Date\tTemperature");
            foreach (var row in enumerableOfData)
            {
                Console.WriteLine($"{row.Date.ToString("d")}" +
                $"\t{row.Temperature}");
            }
            Console.WriteLine();
            // Expected output:
            //  Date    Temperature
            //  1/2/2012        36
            //  1/3/2012        36
            //  1/4/2012        34
            //  1/5/2012        35
            //  1/6/2012        35
            //  1/7/2012        39
            //  1/8/2012        40
            //  1/9/2012        35
            //  1/10/2012       30
            //  1/11/2012       29

            // Skip the first 5 rows in the dataset
            var filteredData = mlContext.Data.SkipRows(data, 5);

            // Look at the filtered data and observe that the first 5 rows have been
            // dropped
            var enumerable = mlContext.Data
                .CreateEnumerable<SampleTemperatureData>(filteredData,
                reuseRowObject: true);

            Console.WriteLine($"Date\tTemperature");
            foreach (var row in enumerable)
            {
                Console.WriteLine($"{row.Date.ToString("d")}" +
                    $"\t{row.Temperature}");
            }
            // Expected output:
            //  Date    Temperature
            //  1/7/2012        39
            //  1/8/2012        40
            //  1/9/2012        35
            //  1/10/2012       30
            //  1/11/2012       29
        }

        private class SampleTemperatureData
        {
            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
                };

            }
        }
    }
}

Hinweise

Überspringt die ersten count Zeilen von input und gibt eine IDataView mit allen anderen Zeilen zurück.