ConversionsExtensionsCatalog.MapValueToKey Method

Definition

Overloads

MapValueToKey(TransformsCatalog+ConversionTransforms, InputOutputColumnPair[], Int32, ValueToKeyMappingEstimator+KeyOrdinality, Boolean, IDataView)

Create a ValueToKeyMappingEstimator, which converts value types into keys.

MapValueToKey(TransformsCatalog+ConversionTransforms, String, String, Int32, ValueToKeyMappingEstimator+KeyOrdinality, Boolean, IDataView)

Create a ValueToKeyMappingEstimator, which converts value types into keys.

MapValueToKey(TransformsCatalog+ConversionTransforms, InputOutputColumnPair[], Int32, ValueToKeyMappingEstimator+KeyOrdinality, Boolean, IDataView)

Create a ValueToKeyMappingEstimator, which converts value types into keys.

public static Microsoft.ML.Transforms.ValueToKeyMappingEstimator MapValueToKey (this Microsoft.ML.TransformsCatalog.ConversionTransforms catalog, Microsoft.ML.InputOutputColumnPair[] columns, int maximumNumberOfKeys = 1000000, Microsoft.ML.Transforms.ValueToKeyMappingEstimator.KeyOrdinality keyOrdinality = Microsoft.ML.Transforms.ValueToKeyMappingEstimator+KeyOrdinality.ByOccurrence, bool addKeyValueAnnotationsAsText = false, Microsoft.ML.IDataView keyData = null);
static member MapValueToKey : Microsoft.ML.TransformsCatalog.ConversionTransforms * Microsoft.ML.InputOutputColumnPair[] * int * Microsoft.ML.Transforms.ValueToKeyMappingEstimator.KeyOrdinality * bool * Microsoft.ML.IDataView -> Microsoft.ML.Transforms.ValueToKeyMappingEstimator

Parameters

catalog
TransformsCatalog.ConversionTransforms

The conversion transform's catalog.

columns
InputOutputColumnPair[]

The input and output columns. The input data types can be numeric, text, boolean, DateTime or DateTimeOffset.

maximumNumberOfKeys
Int32

Maximum number of keys to keep per column when auto-training.

keyOrdinality
ValueToKeyMappingEstimator.KeyOrdinality

How items should be ordered when vectorized. If ByOccurrence chosen they will be in the order encountered. If ByValue, items are sorted according to their default comparison, for example, text sorting will be case sensitive (for example, 'A' then 'Z' then 'a').

addKeyValueAnnotationsAsText
Boolean

Whether key value annotations should be text, regardless of the actual input type.

keyData
IDataView

The data view containing the terms. If specified, this should be a single column data view, and the key-values will be taken from that column. If unspecified, the key-values will be determined from the input data upon fitting.

Returns

Examples

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

namespace Samples.Dynamic
{
    public static class MapValueToKeyMultiColumn
    {
        /// This example demonstrates the use of the ValueToKeyMappingEstimator, by
        /// mapping strings to KeyType values. For more on ML.NET KeyTypes see:
        /// https://github.com/dotnet/machinelearning/blob/master/docs/code/IDataViewTypeSystem.md#key-types 
        /// It is possible to have multiple values map to the same category.
        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();

            // Get a small dataset as an IEnumerable.
            var rawData = new[] {
                new DataPoint() { StudyTime = "0-4yrs" , Course = "CS" },
                new DataPoint() { StudyTime = "6-11yrs" , Course = "CS" },
                new DataPoint() { StudyTime = "12-25yrs" , Course = "LA" },
                new DataPoint() { StudyTime = "0-5yrs" , Course = "DS" }
            };

            var data = mlContext.Data.LoadFromEnumerable(rawData);

            // Constructs the ML.net pipeline
            var pipeline = mlContext.Transforms.Conversion.MapValueToKey(new[] {
                new  InputOutputColumnPair("StudyTimeCategory", "StudyTime"),
                new  InputOutputColumnPair("CourseCategory", "Course")
                },
                keyOrdinality: Microsoft.ML.Transforms.ValueToKeyMappingEstimator
                    .KeyOrdinality.ByValue, addKeyValueAnnotationsAsText: true);

            // Fits the pipeline to the data.
            IDataView transformedData = pipeline.Fit(data).Transform(data);

            // Getting the resulting data as an IEnumerable.
            // This will contain the newly created columns.
            IEnumerable<TransformedData> features = mlContext.Data.CreateEnumerable<
                TransformedData>(transformedData, reuseRowObject: false);

            Console.WriteLine($" StudyTime   StudyTimeCategory   Course    " +
                $"CourseCategory");

            foreach (var featureRow in features)
                Console.WriteLine($"{featureRow.StudyTime}\t\t" +
                    $"{featureRow.StudyTimeCategory}\t\t\t{featureRow.Course}\t\t" +
                    $"{featureRow.CourseCategory}");

            // TransformedData obtained post-transformation.
            //
            // StudyTime     StudyTimeCategory   Course    CourseCategory
            // 0-4yrs          1                   CS          1
            // 6-11yrs         4                   CS          1
            // 12-25yrs        3                   LA          3
            // 0-5yrs          2                   DS          2

            // If we wanted to provide the mapping, rather than letting the
            // transform create it, we could do so by creating an IDataView one
            // column containing the values to map to. If the values in the dataset
            // are not found in the lookup IDataView they will get mapped to the
            // mising value, 0. The keyData are shared among the columns, therefore
            // the keys are not contiguous for the column. Create the lookup map
            // data IEnumerable.  
            var lookupData = new[] {
                new LookupMap { Key = "0-4yrs" },
                new LookupMap { Key = "6-11yrs" },
                new LookupMap { Key = "25+yrs"  },
                new LookupMap { Key = "CS" },
                new LookupMap { Key = "DS" },
                new LookupMap { Key = "LA"  }
            };

            // Convert to IDataView
            var lookupIdvMap = mlContext.Data.LoadFromEnumerable(lookupData);

            // Constructs the ML.net pipeline
            var pipelineWithLookupMap = mlContext.Transforms.Conversion
                .MapValueToKey(new[] {
                    new  InputOutputColumnPair("StudyTimeCategory", "StudyTime"),
                    new  InputOutputColumnPair("CourseCategory", "Course")
                    },
                    keyData: lookupIdvMap);

            // Fits the pipeline to the data.
            transformedData = pipelineWithLookupMap.Fit(data).Transform(data);

            // Getting the resulting data as an IEnumerable.
            // This will contain the newly created columns.
            features = mlContext.Data.CreateEnumerable<TransformedData>(
                transformedData, reuseRowObject: false);

            Console.WriteLine($" StudyTime   StudyTimeCategory  " +
                $"Course CourseCategory");

            foreach (var featureRow in features)
                Console.WriteLine($"{featureRow.StudyTime}\t\t" +
                    $"{featureRow.StudyTimeCategory}\t\t\t{featureRow.Course}\t\t" +
                    $"{featureRow.CourseCategory}");

            // StudyTime    StudyTimeCategory  Course     CourseCategory
            // 0 - 4yrs          1              CS              4
            // 6 - 11yrs         2              CS              4
            // 12 - 25yrs        0              LA              6
            // 0 - 5yrs          0              DS              5

        }

        private class DataPoint
        {
            public string StudyTime { get; set; }
            public string Course { get; set; }
        }

        private class TransformedData : DataPoint
        {
            public uint StudyTimeCategory { get; set; }
            public uint CourseCategory { get; set; }
        }

        // Type for the IDataView that will be serving as the map
        private class LookupMap
        {
            public string Key { get; set; }
        }
    }
}

Remarks

This transform can operate over several columns.

MapValueToKey(TransformsCatalog+ConversionTransforms, String, String, Int32, ValueToKeyMappingEstimator+KeyOrdinality, Boolean, IDataView)

Create a ValueToKeyMappingEstimator, which converts value types into keys.

public static Microsoft.ML.Transforms.ValueToKeyMappingEstimator MapValueToKey (this Microsoft.ML.TransformsCatalog.ConversionTransforms catalog, string outputColumnName, string inputColumnName = null, int maximumNumberOfKeys = 1000000, Microsoft.ML.Transforms.ValueToKeyMappingEstimator.KeyOrdinality keyOrdinality = Microsoft.ML.Transforms.ValueToKeyMappingEstimator+KeyOrdinality.ByOccurrence, bool addKeyValueAnnotationsAsText = false, Microsoft.ML.IDataView keyData = null);
static member MapValueToKey : Microsoft.ML.TransformsCatalog.ConversionTransforms * string * string * int * Microsoft.ML.Transforms.ValueToKeyMappingEstimator.KeyOrdinality * bool * Microsoft.ML.IDataView -> Microsoft.ML.Transforms.ValueToKeyMappingEstimator

Parameters

catalog
TransformsCatalog.ConversionTransforms

The conversion transform's catalog.

outputColumnName
String

Name of the column resulting from the transformation of inputColumnName.

inputColumnName
String

Name of the column to transform. If set to null, the value of the outputColumnName will be used as source. The input data types can be numeric, text, boolean, DateTime or DateTimeOffset.

maximumNumberOfKeys
Int32

Maximum number of keys to keep per column when auto-training.

keyOrdinality
ValueToKeyMappingEstimator.KeyOrdinality

How items should be ordered when vectorized. If ByOccurrence chosen they will be in the order encountered. If ByValue, items are sorted according to their default comparison, for example, text sorting will be case sensitive (for example, 'A' then 'Z' then 'a').

addKeyValueAnnotationsAsText
Boolean

Whether key value annotations should be text, regardless of the actual input type.

keyData
IDataView

The data view containing the terms. If specified, this should be a single column data view, and the key-values will be taken from that column. If unspecified, the key-values will be determined from the input data upon fitting.

Returns

Examples

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

namespace Samples.Dynamic
{
    public class KeyToValueToKey
    {
        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();

            // Get a small dataset as an IEnumerable.
            var rawData = new[] {
                new DataPoint() { Review = "animals birds cats dogs fish horse"},
                new DataPoint() { Review = "horse birds house fish duck cats"},
                new DataPoint() { Review = "car truck driver bus pickup"},
                new DataPoint() { Review = "car truck driver bus pickup horse"},
            };

            var trainData = mlContext.Data.LoadFromEnumerable(rawData);

            // A pipeline to convert the terms of the 'Review' column in 
            // making use of default settings.
            var defaultPipeline = mlContext.Transforms.Text.TokenizeIntoWords(
                "TokenizedText", nameof(DataPoint.Review)).Append(mlContext
                .Transforms.Conversion.MapValueToKey(nameof(TransformedData.Keys),
                "TokenizedText"));

            // Another pipeline, that customizes the advanced settings of the
            // ValueToKeyMappingEstimator. We can change the maximumNumberOfKeys to
            // limit how many keys will get generated out of the set of words, and
            // condition the order in which they get evaluated by changing
            // keyOrdinality from the default ByOccurence (order in which they get
            // encountered) to value/alphabetically.
            var customizedPipeline = mlContext.Transforms.Text.TokenizeIntoWords(
                "TokenizedText", nameof(DataPoint.Review)).Append(mlContext
                .Transforms.Conversion.MapValueToKey(nameof(TransformedData.Keys),
                "TokenizedText", maximumNumberOfKeys: 10, keyOrdinality:
                ValueToKeyMappingEstimator.KeyOrdinality.ByValue));

            // The transformed data.
            var transformedDataDefault = defaultPipeline.Fit(trainData).Transform(
                trainData);

            var transformedDataCustomized = customizedPipeline.Fit(trainData)
                .Transform(trainData);

            // Getting the resulting data as an IEnumerable.
            // This will contain the newly created columns.
            IEnumerable<TransformedData> defaultData = mlContext.Data.
                CreateEnumerable<TransformedData>(transformedDataDefault,
                reuseRowObject: false);

            IEnumerable<TransformedData> customizedData = mlContext.Data.
                CreateEnumerable<TransformedData>(transformedDataCustomized,
                reuseRowObject: false);

            Console.WriteLine($"Keys");
            foreach (var dataRow in defaultData)
                Console.WriteLine($"{string.Join(',', dataRow.Keys)}");
            // Expected output:
            //  Keys
            //  1,2,3,4,5,6
            //  6,2,7,5,8,3
            //  9,10,11,12,13
            //  9,10,11,12,13,6

            Console.WriteLine($"Keys");
            foreach (var dataRow in customizedData)
                Console.WriteLine($"{string.Join(',', dataRow.Keys)}");
            // Expected output:
            //  Keys
            //  1,2,4,5,7,8
            //  8,2,9,7,6,4
            //  3,10,0,0,0
            //  3,10,0,0,0,8
            // Retrieve the original values, by appending the KeyToValue etimator to
            // the existing pipelines to convert the keys back to the strings.
            var pipeline = defaultPipeline.Append(mlContext.Transforms.Conversion
                .MapKeyToValue(nameof(TransformedData.Keys)));

            transformedDataDefault = pipeline.Fit(trainData).Transform(trainData);

            // Preview of the DefaultColumnName column obtained.
            var originalColumnBack = transformedDataDefault.GetColumn<VBuffer<
                ReadOnlyMemory<char>>>(transformedDataDefault.Schema[nameof(
                TransformedData.Keys)]);

            foreach (var row in originalColumnBack)
            {
                foreach (var value in row.GetValues())
                    Console.Write($"{value} ");
                Console.WriteLine("");
            }

            // Expected output:
            //  animals birds cats dogs fish horse
            //  horse birds house fish duck cats
            //  car truck driver bus pickup
            //  car truck driver bus pickup horse
        }

        private class DataPoint
        {
            public string Review { get; set; }
        }

        private class TransformedData : DataPoint
        {
            public uint[] Keys { get; set; }
        }
    }
}

Applies to