private static Action <TermTransform.TermMap> Wrap <T>(ToKeyFitResult <T> .OnFit onFit)
{
if (onFit == null)
{
return(null);
}
// The type T asociated with the delegate will be the actual value type once #863 goes in.
// However, until such time as #863 goes in, it would be too awkward to attempt to extract the metadata.
// For now construct the useless object then pass it into the delegate.
return(map => onFit(new ToKeyFitResult <T>(map)));
}
/// <summary>
/// Converts the categorical value into an indicator array by building a dictionary of categories based on the data and using the id in the dictionary as the index in the array.
/// </summary>
/// <param name="input">Incoming data.</param>
/// <param name="outputKind">Specify the output type of indicator array: Multiarray, array or binary encoded data.</param>
/// <param name="order">How the Id for each value would be assigined: by occurrence or by value.</param>
/// <param name="maxItems">Maximum number of ids to keep during data scanning.</param>
/// <param name="onFit">Called upon fitting with the learnt enumeration on the dataset.</param>
public static Vector <float> OneHotEncoding(this Vector <string> input, OneHotVectorOutputKind outputKind = DefOut, KeyValueOrder order = DefSort, int maxItems = DefMax,
ToKeyFitResult <ReadOnlyMemory <char> > .OnFit onFit = null)
{
Contracts.CheckValue(input, nameof(input));
return(new ImplVector <string>(input, new Config(outputKind, order, maxItems, Wrap(onFit))));
}