/// <summary>
/// Safely gets all class labels.
/// </summary>
/// <typeparam name="TInstanceSource">The type of a source of instances.</typeparam>
/// <typeparam name="TInstance">The type of an instance.</typeparam>
/// <typeparam name="TLabelSource">The type of a source of labels.</typeparam>
/// <typeparam name="TLabel">The type of a label.</typeparam>
/// <param name="mapping">The mapping.</param>
/// <param name="instanceSource">An optional instance source.</param>
/// <param name="labelSource">An optional label source.</param>
/// <returns>All possible values of a label.</returns>
/// <exception cref="MappingException">Thrown if the class labels are null, empty, identical or not unique.</exception>
public static IEnumerable <TLabel> GetClassLabelsSafe <TInstanceSource, TInstance, TLabelSource, TLabel>(
this IClassifierEvaluatorMapping <TInstanceSource, TInstance, TLabelSource, TLabel> mapping,
TInstanceSource instanceSource = default(TInstanceSource),
TLabelSource labelSource = default(TLabelSource))
{
IEnumerable <TLabel> classLabels = mapping.GetClassLabels(instanceSource, labelSource);
if (classLabels == null)
{
throw new MappingException("The class labels must not be null.");
}
IList <TLabel> classLabelList = classLabels.ToList();
if (classLabelList.Any(label => label == null))
{
throw new MappingException("A class label must not be null.");
}
var classLabelSet = new HashSet <TLabel>(classLabelList);
int uniqueClassLabelCount = classLabelSet.Count;
if (uniqueClassLabelCount != classLabelList.Count)
{
throw new MappingException("All class labels must be unique.");
}
if (uniqueClassLabelCount < 2)
{
throw new MappingException("There must be at least two distinct class labels.");
}
return(classLabelList);
}
/// <summary>
/// Safely retrieves the label for a given instance.
/// </summary>
/// <typeparam name="TInstanceSource">The type of a source of instances.</typeparam>
/// <typeparam name="TInstance">The type of an instance.</typeparam>
/// <typeparam name="TLabelSource">The type of a source of labels.</typeparam>
/// <typeparam name="TLabel">The type of a label.</typeparam>
/// <param name="mapping">The mapping.</param>
/// <param name="instance">The instance to provide the label for.</param>
/// <param name="instanceSource">An optional source of instances.</param>
/// <param name="labelSource">An optional source of labels.</param>
/// <returns>The label of the given instance.</returns>
/// <exception cref="MappingException">Thrown if the retrieved label is null.</exception>
public static TLabel GetLabelSafe <TInstanceSource, TInstance, TLabelSource, TLabel>(
this IClassifierEvaluatorMapping <TInstanceSource, TInstance, TLabelSource, TLabel> mapping,
TInstance instance,
TInstanceSource instanceSource = default(TInstanceSource),
TLabelSource labelSource = default(TLabelSource))
{
TLabel label = mapping.GetLabel(instance, instanceSource, labelSource);
if (label == null)
{
throw new MappingException("The label must not be null.");
}
return(label);
}
/// <summary>
/// Safely retrieves instances for a given instance source.
/// </summary>
/// <typeparam name="TInstanceSource">The type of a source of instances.</typeparam>
/// <typeparam name="TInstance">The type of an instance.</typeparam>
/// <typeparam name="TLabelSource">The type of a source of labels.</typeparam>
/// <typeparam name="TLabel">The type of a label.</typeparam>
/// <param name="mapping">The mapping.</param>
/// <param name="instanceSource">The source of instances.</param>
/// <returns>The instances provided by the instance source.</returns>
/// <exception cref="MappingException">Thrown if the retrieved instances are null.</exception>
public static IEnumerable <TInstance> GetInstancesSafe <TInstanceSource, TInstance, TLabelSource, TLabel>(
this IClassifierEvaluatorMapping <TInstanceSource, TInstance, TLabelSource, TLabel> mapping,
TInstanceSource instanceSource)
{
IEnumerable <TInstance> instances = mapping.GetInstances(instanceSource);
if (instances == null)
{
throw new MappingException("The instances must not be null.");
}
if (instances.Any(instance => instance == null))
{
throw new MappingException("An instance must not be null.");
}
return(instances);
}
