- introduced ROC curves

src/fr/inrialpes/exmo/align/impl/eval/ROCCurveEvaluator.java

+/*
+ * $Id$
+ *
+ * Copyright (C) INRIA, 2004-2005, 2007-2010
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
+
+package fr.inrialpes.exmo.align.impl.eval;
+
+import org.semanticweb.owl.align.Alignment;
+import org.semanticweb.owl.align.AlignmentException;
+import org.semanticweb.owl.align.Cell;
+
+import java.util.Enumeration;
+import java.util.Properties;
+import java.util.Iterator;
+import java.util.TreeSet;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.Comparator;
+import java.util.Vector;
+import java.io.PrintWriter;
+import java.net.URI;
+
+/**
+ * Compute ROCCurves
+ * The first alignment is thus the expected one
+ *
+ * @author Jerome Euzenat
+ * @version $Id$ 
+ * 
+ * ROCCurves traverse the ranked list of correspondences
+ * Hence, like PRGraphs, it is only relevant to this case.
+ * X-axis is the number of incorrect correspondences
+ * Y-axis is the number of correct correspondences
+ * It is expected that the curve grows fast first and then much slower
+ * This indicates the accuracy of the matcher.
+ *
+ * The "Surface Under Curve" (AUC) is returned as a result.
+ * AUC is in fact the percentage of surface under the curve (given by N the size of the reference alignment and P the size of all pairs of ontologies, N*P is the full size), Area/N*P.
+ * It is ususally interpreted as:
+ * 0.9 - 1.0 excellent
+ * 0.8 - 0.9 good
+ * 0.7 - 0.8 fair
+ * 0.6 - 0.7 poor
+ * 0.0 - 0.6 bad
+ *
+ * The problem with these measures is that they assume that the provided alignment
+ * is a complete alignment: it contains all pairs of entities hence auc are comparable
+ * because they depend on the same sizes... This is not the case when alignment are
+ * incomplete. Hence, this should be normalised.
+ *
+ * There are two ways of doing this:
+ * - simply Area/N*P, but this would advantage
+ * - considering the current subpart Area/N*|
+ *   => both would advantage matchers with high precision
+ * penalising them Area/N*P
+ * - interpolating the curve: 
+ * NOT EASY, TO BE IMPLEMENTED
+ */
+
+public class ROCCurveEvaluator extends GraphEvaluator {
+
+    private double auc = 0.0;
+
+    public ROCCurveEvaluator( Alignment align1, Alignment align2 ) {
+	super(align1, align2);
+    }
+
+    /**
+     * Compute ROCCurve
+     */
+    public double eval( Properties params ) throws AlignmentException {
+	return eval( params, (Object)null );
+    }
+    public double eval( Properties params, Object cache ) throws AlignmentException {
+	// Local variables
+	int nbfound = 0;
+	int area = 0;
+	int x = 0;
+	int y = 0;
+	
+	int scale = align2.nbCells();
+
+	points = new Vector<Pair>();
+
+	// Create a sorted structure in which putting the cells
+	// TreeSet could be replaced by something else
+	SortedSet<Cell> cellSet = orderAlignment();
+
+	// Collect the points in the curve
+	points.add( new Pair( 0., 0. ) ); // [Origin]
+	for( Cell c2 : cellSet ) {
+	    nbfound++;
+	    if ( correctCell( c2, align2, align1 ) > 0. ) {
+		y++; 
+	    } else {
+		x++;  area += y;
+	    }
+	    points.add( new Pair( x, y ) );
+	}
+	auc = (double)area / (double)nbfound;
+
+	return auc;
+    }
+
+    /**
+     * This output the result
+     */
+    public void write(PrintWriter writer) throws java.io.IOException {
+	writer.println("<?xml version='1.0' encoding='utf-8' standalone='yes'?>");
+	writer.println("<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>");
+	writer.println("  <output rdf:about=''>");
+	writeXMLMap( writer );
+	writer.print("    <AUC>"+auc+"</AUC>\n");
+	writer.print("  </output>\n</rdf:RDF>\n");
+    }
+    
+    public void writePlot(PrintWriter writer) {
+	writeFullPlot( writer );
+    }
+    
+    public double getAUC(){
+	return auc;
+    }
+}
+