/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.com
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.preprocessing.outlier;
import java.util.Iterator;
import java.util.List;
import com.rapidminer.example.Attribute;
import com.rapidminer.example.Example;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.example.table.AttributeFactory;
import com.rapidminer.operator.IOObject;
import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.parameter.ParameterType;
import com.rapidminer.parameter.ParameterTypeCategory;
import com.rapidminer.parameter.ParameterTypeInt;
import com.rapidminer.tools.Ontology;
/**
* <p>This operator performs a LOF outlier search. LOF outliers or outliers with a local
* outlier factor per object are density based outliers according to Breuning,
* Kriegel, et al.</p>
*
* <p>The approach to find those outliers is based on measuring the density of objects
* and its relation to each other (referred to as local reachability density).
* Based on the average ratio of the local reachability density of an object and its
* k-nearest neighbours (e.g. the objects in its k-distance neighbourhood), a local
* outlier factor (LOF) is computed. The approach takes a parameter MinPts
* (actually specifying the "k") and it uses the maximum LOFs for objects in a MinPts range
* (lower bound and upper bound to MinPts).</p>
*
* <p>Currently, the operator supports cosine, sine or squared distances in addition
* to the usual euclidian distance which can be specified by the corresponding parameter.
* In the first step, the objects are grouped into containers. For each object, using a
* radius screening of all other objects, all the available distances between that object
* and another object (or group of objects) on the (same) radius given by the
* distance are associated with a container. That container than has the distance
* information as well as the list of objects within that distance (usually only a few)
* and the information, how many objects are in the container.</p>
*
* <p>In the second step, three things are done: (1) The containers for each object are counted
* in acending order according to the cardinality of the object list within the container
* (= that distance) to find the k-distances for each object and the
* objects in that k-distance (all objects in all the subsequent containers with a smaller
* distance). (2) Using this information, the local reachability densities are computed by
* using the maximum of the actual distance and the k-distance for each
* object pair (object and objects in k-distance) and averaging it by the cardinality of
* the k-neighbourhood and than taking the reciprocal value. (3) The LOF is computed for
* each MinPts value in the range (actually for all up to upper bound) by
* averaging the ratio between the MinPts-local reachability-density of all objects in
* the k-neighbourhood and the object itself. The maximum LOF in the MinPts range is
* passed as final LOF to each object.</p>
*
* <p>Afterwards LOFs are added as values for a special real-valued outlier attribute
* in the example set which the operator will return.</p>
*
* @author Stephan Deutsch, Ingo Mierswa
* @version $Id: LOFOutlierOperator.java,v 1.5 2008/07/07 07:06:46 ingomierswa Exp $
*/
public class LOFOutlierOperator extends Operator {
/** The parameter name for "The lower bound for MinPts for the Outlier test " */
public static final String PARAMETER_MINIMAL_POINTS_LOWER_BOUND = "minimal_points_lower_bound";
/** The parameter name for "The upper bound for MinPts for the Outlier test " */
public static final String PARAMETER_MINIMAL_POINTS_UPPER_BOUND = "minimal_points_upper_bound";
/** The parameter name for "choose which distance function will be used for calculating " */
public static final String PARAMETER_DISTANCE_FUNCTION = "distance_function";
private static final String[] distanceFunctionList = {
"euclidian distance",
"squared distance",
"cosine distance",
"inverted cosine distance",
"angle"
};
public LOFOutlierOperator(OperatorDescription description) {
super(description);
}
/**
* This method implements the main functionality of the Operator but can be considered
* as a sort of wrapper to pass the RapidMiner operator chain data deeper into the
* SearchSpace class, so do not expect a lot of things happening here.
*/
public IOObject[] apply() throws OperatorException {
// declaration and initializing the necessary fields from input
int minPtsLowerBound = 0;
int minPtsUpperBound = 0;
int minPtsLB = this.getParameterAsInt(PARAMETER_MINIMAL_POINTS_LOWER_BOUND);
int minPtsUB = this.getParameterAsInt(PARAMETER_MINIMAL_POINTS_UPPER_BOUND);
int kindOfDistance = this.getParameterAsInt(PARAMETER_DISTANCE_FUNCTION);
// check for the sanity of entered parameters:
if (minPtsLB <= minPtsUB) { // if lower bound is smaller or equal upper bound, pass them on
minPtsLowerBound = minPtsLB;
minPtsUpperBound = minPtsUB;
} else { // else change both to have a sensible set of parameters ;-)
minPtsLowerBound = minPtsUB;
minPtsUpperBound = minPtsLB;
}
// create a new SearchSpace for the LOF-Outlier search
ExampleSet eSet = getInput(ExampleSet.class);
Iterator<Example> reader = eSet.iterator();
int searchSpaceDimension = eSet.getAttributes().size();
SearchSpace sr = new SearchSpace(searchSpaceDimension, minPtsLowerBound, minPtsUpperBound + 1);
// now read through the Examples of the ExampleSet
int counter = 0;
while (reader.hasNext()) {
Example example = reader.next(); // read the next example & create a search object
SearchObject so = new SearchObject(searchSpaceDimension, "object" + counter, minPtsLowerBound, minPtsUpperBound);
// for now, give so an id like label and add the MinPts ranges, so that arrays are initialized
counter++;
int i = 0;
for (Attribute attribute : eSet.getAttributes()) {
so.setVektor(i++, example.getValue(attribute));
}
sr.addObject(so); // finally add the search object to the search room
}
log("Searching d=" + sr.getDimensions() + " dimensions with" + " MinPts Interval [" + minPtsLowerBound + " ; " + minPtsUpperBound + "]");
// set all Outlier Factors to ZERO to be sure
sr.resetOutlierStatus();
// find all Containers for the LOF first
sr.findAllKdContainers(kindOfDistance);
// perform the LOF-Outlier search
sr.computeLOF(minPtsLowerBound, minPtsUpperBound);
Attribute outlierAttribute = AttributeFactory.createAttribute("Outlier", Ontology.REAL);
eSet.getExampleTable().addAttribute(outlierAttribute);
eSet.getAttributes().setOutlier(outlierAttribute);
counter = 0; // reset counter to zero
Iterator<Example> reader2 = eSet.iterator();
while (reader2.hasNext()) {
Example example = reader2.next(); // read the next example
SearchObject sobj = sr.getSearchObjects().elementAt(counter);
example.setValue(outlierAttribute, sobj.getOutlierFactor());
counter++;
}
return new IOObject[] { eSet };
}
/**
* This method override specifies the LOFOutlierOperator to take an ExampleSet as input.
*/
public Class<?>[] getInputClasses() {
return new Class[] { ExampleSet.class };
}
/**
* This method override specifies the LOFOutlierOperator to probide an ExampleSet
* as output. (please note, that the output ExampleSets will be a modified version
* of the input ExampleSet, e.g. a predicted label will be added representing the
* outlier factor (double value).
*/
public Class<?>[] getOutputClasses() {
return new Class[] { ExampleSet.class };
}
public List<ParameterType> getParameterTypes() {
List<ParameterType> types = super.getParameterTypes();
types.add(new ParameterTypeInt(PARAMETER_MINIMAL_POINTS_LOWER_BOUND, "The lower bound for MinPts for the Outlier test " + "(default value is 10)", 0, Integer.MAX_VALUE, 10));
types.add(new ParameterTypeInt(PARAMETER_MINIMAL_POINTS_UPPER_BOUND, "The upper bound for MinPts for the Outlier test " + "(default value is 20)", 0, Integer.MAX_VALUE, 20));
types.add(new ParameterTypeCategory(PARAMETER_DISTANCE_FUNCTION, "choose which distance function will be used for calculating " + "the distance between two objects", distanceFunctionList, 0));
return types;
}
}