/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* InstancesComparator.java
* Copyright (C) 2004 Stijn Lievens
*
*/
package weka.classifiers.misc.monotone;
import weka.core.Instance;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import java.util.Comparator;
/**
* Class to compare instances with respect to a given attribute, indicated
* by its index. The ordering of the attribute values is determined
* by the internal values of WEKA. There is also the possibility of
* reversing this order.
* <p>
* This implementation is part of the master's thesis: "Studie
* en implementatie van instantie-gebaseerde algoritmen voor gesuperviseerd
* rangschikken", Stijn Lievens, Ghent University, 2004.
* </p>
*
* @author Stijn Lievens (stijn.lievens@ugent.be)
* @version $Revision: 1.2 $
*/
public class InstancesComparator
implements Comparator, RevisionHandler {
/** index of the attribute */
private int m_Index;
/** If 1 then the order is not reversed, when -1, the order is reversed */
private int m_Reverse = 1;
/**
* Construct an <code> InstancesComparator </code> that compares
* the attributes with the given index.
*
* @param index the index on which to compare instances
*/
public InstancesComparator(int index) {
m_Index = index;
}
/**
* Construct an <code> InstancesComparator </code> that compares
* the attributes with the given index, with the possibility of
* reversing the order.
*
* @param index the index on which to compare instances
* @param reverse if <code> true </code> the order is reversed, if
* <code> false </code> the order is not reversed
*/
public InstancesComparator(int index, boolean reverse) {
m_Index = index;
m_Reverse = (reverse == true) ? -1 : 1;
}
/**
* Compares two objects (instances) with respect to the attribute
* this comparator is constructed on.
*
* @param o1 the first object to be compared
* @param o2 the second object to be compared
* @return -1 if <code> o1 < o2 </code> (wrt to the given attribute),
* 1 if <code> o1 > o2 </code>, and 0 if <code> o1 </code> and
* <code> o2 </code> are equal (wrt to the given attribute)
*/
public int compare(Object o1, Object o2) {
Instance i1 = (Instance) o1;
Instance i2 = (Instance) o2;
if (i1.value(m_Index) < i2.value(m_Index)) {
return -1 * m_Reverse;
} else if (i1.value(m_Index) > i2.value(m_Index)) {
return 1 * m_Reverse;
}
return 0;
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 1.2 $");
}
}