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EuclideanDissimilarity.cs
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/*
* Created by: Miguel Angel Medina Pérez (miguelmedinaperez@gmail.com)
* Created: 05/18/2007
* Comments by: Miguel Angel Medina Pérez (miguelmedinaperez@gmail.com)
*/
using System;
using System.Collections.Generic;
using System.Linq;
using PRFramework.Core.Common;
using PRFramework.Core.SupervisedClassifiers;
namespace PRFramework.Core.ComparisonFunctions
{
/// <summary>
/// A generic implementation of Euclidean distance with normalization.
/// </summary>
/// <remarks>
/// <para>
/// The constructor of the class requires a delegate <see cref="GetComponent{IVector}"/> to provide the values of the components of the vectors.
/// </para>
/// <para>
/// Las diferencias entre los valores de un componente se normalizan por la diferencia del valor máximo menos el valor mínimo de dicho componente.
/// </para>
/// </remarks>
/// <typeparam name="IVector">A type of vector.</typeparam>
[Serializable]
public class EuclideanDissimilarity
{
public EuclideanDissimilarity(IEnumerable<Instance> instances, InstanceModel model)
{
_instanceModel = model;
var classFeature = model.ClassFeature();
_features = _instanceModel.Features.Where(f => f != classFeature).ToList();
int instanceCount = 0;
foreach (var instance in instances)
{
if (_instanceModel != instance.Model)
throw new ArgumentOutOfRangeException(nameof(model), model, $"Unable to instantiate ${nameof(EuclideanDissimilarity)}: Object found with invalid ${nameof(InstanceModel)}.");
if (_minFeatureValues != null)
{
foreach (var feature in _features)
if (!Double.IsNaN(instance[feature]))
{
if (feature.FeatureType == FeatureType.Double || feature.FeatureType == FeatureType.Integer)
{
if (Double.IsNaN(_minFeatureValues[feature.Index]) || instance[feature] < _minFeatureValues[feature.Index])
_minFeatureValues[feature.Index] = instance[feature];
if (Double.IsNaN(_maxFeatureValues[feature.Index]) || instance[feature] > _maxFeatureValues[feature.Index])
_maxFeatureValues[feature.Index] = instance[feature];
}
}
}
else
{
_minFeatureValues = new double[_features.Count];
_maxFeatureValues = new double[_features.Count];
foreach (var feature in _features)
if (Double.IsNaN(instance[feature]))
{
_minFeatureValues[feature.Index] = Double.NaN;
_maxFeatureValues[feature.Index] = Double.NaN;
}
else
{
if (feature.FeatureType == FeatureType.Double || feature.FeatureType == FeatureType.Integer)
{
_minFeatureValues[feature.Index] = instance[feature];
_maxFeatureValues[feature.Index] = instance[feature];
}
else if (feature.FeatureType == FeatureType.Nominal)
{
_minFeatureValues[feature.Index] = Double.NaN;
_maxFeatureValues[feature.Index] = Double.NaN;
}
}
}
instanceCount++;
}
if (instanceCount < 1)
throw new ArgumentOutOfRangeException(nameof(instances), instances, $"Unable to instantiate ${nameof(EuclideanDissimilarity)}: empty vector collection.");
_maxLessMin = new double[_minFeatureValues.Length];
double validFeaturesCount = 0;
for (int i = 0; i < _minFeatureValues.Length; i++)
{
_maxLessMin[i] = _maxFeatureValues[i] - _minFeatureValues[i];
if (!Double.IsNaN(_maxLessMin[i]) || (_features[i].FeatureType == FeatureType.Nominal))
validFeaturesCount++;
}
_maxDissimilarity = Math.Sqrt(validFeaturesCount);
}
//public static List<NormalizedEuclideanDistance> CreateDistances(IList<Instance> instances,
// IEnumerable<IList<Feature>> collectionOfFeaturesCollections, InstanceModel model)
//{
// if (collectionOfFeaturesCollections == null)
// throw new ArgumentNullException(nameof(collectionOfFeaturesCollections), $"Unable to instantiate ${nameof(NormalizedEuclideanDistance)}: null collection of features collections.");
// var distancesList = new List<NormalizedEuclideanDistance>();
// foreach (var featuresCollection in collectionOfFeaturesCollections)
// distancesList.Add(distancesList.Count == 0
// ? new NormalizedEuclideanDistance(instances, featuresCollection, model)
// : new NormalizedEuclideanDistance(distancesList[0]._maxLessMin, featuresCollection, model));
// return distancesList;
//}
public double Compare(Instance source, Instance compareTo)
{
try
{
double sum = 0;
foreach (var feature in _features)
if (!Double.IsNaN(source[feature]) && !Double.IsNaN(compareTo[feature]))
{
if (feature.FeatureType == FeatureType.Double || feature.FeatureType == FeatureType.Integer)
{
if (!double.IsNaN(_maxLessMin[feature.Index]) && _maxLessMin[feature.Index] > 0)
{
double componentDiff = Math.Abs(source[feature] - compareTo[feature]) / _maxLessMin[feature.Index];
sum += componentDiff > 1 ? 1 : Math.Pow(componentDiff, 2);
}
}
else if (feature.FeatureType == FeatureType.Nominal &&
(int)source[feature] != (int)compareTo[feature])
sum += 1;
}
else
sum += 1;
return Math.Sqrt(sum) / _maxDissimilarity;
}
catch (Exception e)
{
if (_instanceModel.Features.Length != source.Model.Features.Length)
throw new ArgumentOutOfRangeException(nameof(source), source,
"Unable to compare objects: Invalid instance model");
if (_instanceModel.Features.Length != compareTo.Model.Features.Length)
throw new ArgumentOutOfRangeException(nameof(compareTo), compareTo,
"Unable to compare objects: Invalid instance model");
for (int i = 0; i < source.Model.Features.Length; i++)
{
if (source.Model.Features[i].FeatureType != _instanceModel.Features[i].FeatureType)
throw new ArgumentOutOfRangeException(nameof(source), source,
"Unable to compare objects: Invalid instance model");
if (compareTo.Model.Features[i].FeatureType != _instanceModel.Features[i].FeatureType)
throw new ArgumentOutOfRangeException(nameof(compareTo), compareTo,
"Unable to compare objects: Invalid instance model");
}
throw;
}
}
public double Compare(Instance source, Instance compareTo, IEnumerable<Feature> featureSubset)
{
try
{
double sum = 0;
double validFeaturesCount = 0;
foreach (var feature in featureSubset)
{
if (!Double.IsNaN(source[feature]) && !Double.IsNaN(compareTo[feature]))
{
if (feature.FeatureType == FeatureType.Double || feature.FeatureType == FeatureType.Integer)
{
if (!double.IsNaN(_maxLessMin[feature.Index]) && _maxLessMin[feature.Index] > 0)
{
double componentDiff = Math.Abs(source[feature] - compareTo[feature]) / _maxLessMin[feature.Index];
sum += componentDiff > 1 ? 1 : Math.Pow(componentDiff, 2);
}
}
else if (feature.FeatureType == FeatureType.Nominal &&
(int)source[feature] != (int)compareTo[feature])
sum += 1;
}
else
sum += 1;
validFeaturesCount++;
}
return Math.Sqrt(sum) / Math.Sqrt(validFeaturesCount);
}
catch (Exception e)
{
if (_instanceModel.Features.Length != source.Model.Features.Length)
throw new ArgumentOutOfRangeException(nameof(source), source,
"Unable to compare objects: Invalid instance model");
if (_instanceModel.Features.Length != compareTo.Model.Features.Length)
throw new ArgumentOutOfRangeException(nameof(compareTo), compareTo,
"Unable to compare objects: Invalid instance model");
for (int i = 0; i < source.Model.Features.Length; i++)
{
if (source.Model.Features[i].FeatureType != _instanceModel.Features[i].FeatureType)
throw new ArgumentOutOfRangeException(nameof(source), source,
"Unable to compare objects: Invalid instance model");
if (compareTo.Model.Features[i].FeatureType != _instanceModel.Features[i].FeatureType)
throw new ArgumentOutOfRangeException(nameof(compareTo), compareTo,
"Unable to compare objects: Invalid instance model");
}
throw;
}
}
public void UpdateTraining(Instance instance)
{
foreach (var feature in _features)
if (!Double.IsNaN(instance[feature]))
{
if (feature.FeatureType == FeatureType.Double || feature.FeatureType == FeatureType.Integer)
{
if (Double.IsNaN(_minFeatureValues[feature.Index]) || instance[feature] < _minFeatureValues[feature.Index])
_minFeatureValues[feature.Index] = instance[feature];
if (Double.IsNaN(_maxFeatureValues[feature.Index]) || instance[feature] > _maxFeatureValues[feature.Index])
_maxFeatureValues[feature.Index] = instance[feature];
}
}
_maxLessMin = new double[_minFeatureValues.Length];
double validFeaturesCount = 0;
for (int i = 0; i < _minFeatureValues.Length; i++)
{
_maxLessMin[i] = _maxFeatureValues[i] - _minFeatureValues[i];
if (!Double.IsNaN(_maxLessMin[i]) || (_features[i].FeatureType == FeatureType.Nominal))
validFeaturesCount++;
}
_maxDissimilarity = Math.Sqrt(validFeaturesCount);
}
private double[] _minFeatureValues = null;
private double[] _maxFeatureValues = null;
private double[] _maxLessMin;
private double _maxDissimilarity;
private readonly List<Feature> _features;
private readonly InstanceModel _instanceModel;
}
}