/// <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>
/// <typeparam name="TFeatures">The type of the features.</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, TFeatures>(
this IPredictorMapping <TInstanceSource, TInstance, TLabelSource, TLabel, TFeatures> mapping,
TInstanceSource instanceSource)
{
IEnumerable <TInstance> instances = mapping.GetInstances(instanceSource);
if (instances == null)
{
throw new MappingException("The instances must not be null.");
}
return(instances);
}
/// <summary>
/// Safely retrieves the features 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>
/// <typeparam name="TFeatures">The type of the features.</typeparam>
/// <param name="mapping">The mapping.</param>
/// <param name="instance">The instance to provide features for.</param>
/// <param name="instanceSource">An optional source of instances.</param>
/// <returns>The features for the given instance.</returns>
/// <exception cref="MappingException">Thrown if the retrieved feature values are null.</exception>
public static TFeatures GetFeaturesSafe <TInstanceSource, TInstance, TLabelSource, TLabel, TFeatures>(
this IPredictorMapping <TInstanceSource, TInstance, TLabelSource, TLabel, TFeatures> mapping,
TInstance instance,
TInstanceSource instanceSource = default(TInstanceSource))
{
TFeatures featureValues = mapping.GetFeatures(instance, instanceSource);
if (featureValues == null)
{
throw new MappingException("The features must not be null.");
}
return(featureValues);
}
/// <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>
/// <typeparam name="TFeatures">The type of the features.</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, TFeatures>(
this IPredictorMapping <TInstanceSource, TInstance, TLabelSource, TLabel, TFeatures> 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);
}
