internal CountTargetEncodingEstimator(IHostEnvironment env, Options options)
{
Contracts.CheckValue(env, nameof(env));
_host = env.Register(nameof(CountTargetEncodingEstimator));
_host.CheckValue(options, nameof(options));
_host.CheckUserArg(Utils.Size(options.Columns) > 0, nameof(options.Columns), "Columns must be specified");
_host.CheckUserArg(!string.IsNullOrWhiteSpace(options.LabelColumn), nameof(options.LabelColumn), "Must specify the label column name");
if (!string.IsNullOrEmpty(options.InitialCountsModel))
{
_countTableEstimator = LoadFromFile(env, options.InitialCountsModel, options.LabelColumn,
options.Columns.Select(col => new InputOutputColumnPair(col.Name)).ToArray());
if (_countTableEstimator == null)
{
throw env.Except($"The file {options.InitialCountsModel} does not contain a CountTableTransformer");
}
}
else if (options.SharedTable)
{
var columns = new CountTableEstimator.SharedColumnOptions[options.Columns.Length];
for (int i = 0; i < options.Columns.Length; i++)
{
var column = options.Columns[i];
columns[i] = new CountTableEstimator.SharedColumnOptions(
column.Name,
column.Name,
column.PriorCoefficient ?? options.PriorCoefficient,
column.LaplaceScale ?? options.LaplaceScale,
column.Seed ?? options.Seed);
}
var builder = options.CountTable;
_host.CheckValue(builder, nameof(options.CountTable));
_countTableEstimator = new CountTableEstimator(_host, options.LabelColumn, builder.CreateComponent(_host), columns);
}
else
{
var columns = new CountTableEstimator.ColumnOptions[options.Columns.Length];
for (int i = 0; i < options.Columns.Length; i++)
{
var column = options.Columns[i];
var builder = column.CountTable ?? options.CountTable;
_host.CheckValue(builder, nameof(options.CountTable));
columns[i] = new CountTableEstimator.ColumnOptions(
column.Name,
column.Name,
builder.CreateComponent(_host),
column.PriorCoefficient ?? options.PriorCoefficient,
column.LaplaceScale ?? options.LaplaceScale,
column.Seed ?? options.Seed);
}
_countTableEstimator = new CountTableEstimator(_host, options.LabelColumn, columns);
}
_hashingColumns = InitializeHashingColumnOptions(options);
_hashingEstimator = new HashingEstimator(_host, _hashingColumns);
}
/// <summary>
/// Transforms a categorical column into a set of features that includes the count of each label class,
/// the log-odds for each label class and the back-off indicator.
/// </summary>
/// <param name="catalog">The transforms catalog.</param>
/// <param name="columns">The input and output columns.</param>
/// <param name="labelColumn">The name of the label column.</param>
/// <param name="builder">The builder that creates the count tables from the training data.</param>
/// <param name="priorCoefficient">The coefficient with which to apply the prior smoothing to the features.</param>
/// <param name="laplaceScale">The Laplacian noise diversity/scale-parameter. Recommended values are between 0 and 1. Note that the noise
/// will only be applied if the estimator is part of an <see cref="EstimatorChain{TLastTransformer}"/>, when fitting the next estimator in the chain.</param>
/// <param name="sharedTable">Indicates whether to keep counts for all columns and slots in one shared count table. If true, the keys in the count table
/// will include a hash of the column and slot indices.</param>
/// <param name="numberOfBits">The number of bits to hash the input into. Must be between 1 and 31, inclusive.</param>
/// <param name="combine">In case the input is a vector column, indicates whether the values should be combined into a single hash to create a single
/// count table, or be left as a vector of hashes with multiple count tables.</param>
/// <param name="hashingSeed">The seed used for hashing the input columns.</param>
/// <returns></returns>
public static CountTargetEncodingEstimator CountTargetEncode(this TransformsCatalog catalog,
InputOutputColumnPair[] columns, string labelColumn = DefaultColumnNames.Label,
CountTableBuilderBase builder = null,
float priorCoefficient = CountTableTransformer.Defaults.PriorCoefficient,
float laplaceScale = CountTableTransformer.Defaults.LaplaceScale,
bool sharedTable = CountTableTransformer.Defaults.SharedTable,
int numberOfBits = HashingEstimator.Defaults.NumberOfBits,
bool combine = HashingEstimator.Defaults.Combine,
uint hashingSeed = HashingEstimator.Defaults.Seed)
{
var env = CatalogUtils.GetEnvironment(catalog);
env.CheckValue(columns, nameof(columns));
builder = builder ?? new CMCountTableBuilder();
CountTargetEncodingEstimator estimator;
if (sharedTable)
{
var columnOptions = new CountTableEstimator.SharedColumnOptions[columns.Length];
for (int i = 0; i < columns.Length; i++)
{
columnOptions[i] = new CountTableEstimator.SharedColumnOptions(
columns[i].OutputColumnName, columns[i].InputColumnName, priorCoefficient, laplaceScale);
}
estimator = new CountTargetEncodingEstimator(env, labelColumn, columnOptions, builder, numberOfBits, combine, hashingSeed);
}
else
{
var columnOptions = new CountTableEstimator.ColumnOptions[columns.Length];
for (int i = 0; i < columns.Length; i++)
{
columnOptions[i] = new CountTableEstimator.ColumnOptions(
columns[i].OutputColumnName, columns[i].InputColumnName, builder, priorCoefficient, laplaceScale);
}
estimator = new CountTargetEncodingEstimator(env, labelColumn, columnOptions, numberOfBits: numberOfBits, combine: combine, hashingSeed: hashingSeed);
}
return(estimator);
}
