/// <summary>
/// Create a new <see cref="IDataView"/> over an enumerable of the items of user-defined type.
/// The user maintains ownership of the <paramref name="data"/> and the resulting data view will
/// never alter the contents of the <paramref name="data"/>.
/// Since <see cref="IDataView"/> is assumed to be immutable, the user is expected to support
/// multiple enumeration of the <paramref name="data"/> that would return the same results, unless
/// the user knows that the data will only be cursored once.
///
/// One typical usage for streaming data view could be: create the data view that lazily loads data
/// as needed, then apply pre-trained transformations to it and cursor through it for transformation
/// results.
/// </summary>
/// <typeparam name="TRow">The user-defined item type.</typeparam>
/// <param name="catalog">The context to use for data view creation.</param>
/// <param name="data">The data to wrap around.</param>
/// <param name="schemaDefinition">The optional schema definition of the data view to create. If <c>null</c>,
/// the schema definition is inferred from <typeparamref name="TRow"/>.</param>
/// <returns>The constructed <see cref="IDataView"/>.</returns>
public static IDataView ReadFromEnumerable <TRow>(this DataOperationsCatalog catalog, IEnumerable <TRow> data, SchemaDefinition schemaDefinition = null)
where TRow : class
{
catalog.Environment.CheckValue(data, nameof(data));
catalog.Environment.CheckValueOrNull(schemaDefinition);
return(DataViewConstructionUtils.CreateFromEnumerable(catalog.Environment, data, schemaDefinition));
}
/// <summary>
/// Create a new <see cref="IDataView"/> over an in-memory collection of the items of user-defined type.
/// The user maintains ownership of the <paramref name="data"/> and the resulting data view will
/// never alter the contents of the <paramref name="data"/>.
/// Since <see cref="IDataView"/> is assumed to be immutable, the user is expected to not
/// modify the contents of <paramref name="data"/> while the data view is being actively cursored.
///
/// One typical usage for in-memory data view could be: create the data view, train a predictor.
/// Once the predictor is fully trained, modify the contents of the underlying collection and
/// train another predictor.
/// </summary>
/// <typeparam name="TRow">The user-defined item type.</typeparam>
/// <param name="env">The host environment to use for data view creation.</param>
/// <param name="data">The data to wrap around.</param>
/// <param name="schemaDefinition">The optional schema definition of the data view to create. If <c>null</c>,
/// the schema definition is inferred from <typeparamref name="TRow"/>.</param>
/// <returns>The constructed <see cref="IDataView"/>.</returns>
public static IDataView CreateDataView <TRow>(this IHostEnvironment env, IList <TRow> data, SchemaDefinition schemaDefinition = null)
where TRow : class
{
Contracts.CheckValue(env, nameof(env));
env.CheckValue(data, nameof(data));
env.CheckValueOrNull(schemaDefinition);
return(DataViewConstructionUtils.CreateFromList(env, data, schemaDefinition));
}
