/*
* 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.
*/
/*
* ClassifierDecList.java
* Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
*
*/
package weka.classifiers.rules.part;
import weka.classifiers.trees.j48.ClassifierSplitModel;
import weka.classifiers.trees.j48.Distribution;
import weka.classifiers.trees.j48.EntropySplitCrit;
import weka.classifiers.trees.j48.ModelSelection;
import weka.classifiers.trees.j48.NoSplit;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import weka.core.Utils;
import java.io.Serializable;
/**
* Class for handling a rule (partial tree) for a decision list.
*
* @author Eibe Frank (eibe@cs.waikato.ac.nz)
* @version $Revision: 1.13 $
*/
public class ClassifierDecList
implements Serializable, RevisionHandler {
/** for serialization */
private static final long serialVersionUID = 7284358349711992497L;
/** Minimum number of objects */
protected int m_minNumObj;
/** To compute the entropy. */
protected static EntropySplitCrit m_splitCrit = new EntropySplitCrit();
/** The model selection method. */
protected ModelSelection m_toSelectModel;
/** Local model at node. */
protected ClassifierSplitModel m_localModel;
/** References to sons. */
protected ClassifierDecList [] m_sons;
/** True if node is leaf. */
protected boolean m_isLeaf;
/** True if node is empty. */
protected boolean m_isEmpty;
/** The training instances. */
protected Instances m_train;
/** The pruning instances. */
protected Distribution m_test;
/** Which son to expand? */
protected int indeX;
/**
* Constructor - just calls constructor of class DecList.
*/
public ClassifierDecList(ModelSelection toSelectLocModel, int minNum){
m_toSelectModel = toSelectLocModel;
m_minNumObj = minNum;
}
/**
* Method for building a pruned partial tree.
*
* @exception Exception if something goes wrong
*/
public void buildRule(Instances data) throws Exception {
buildDecList(data, false);
cleanup(new Instances(data, 0));
}
/**
* Builds the partial tree without hold out set.
*
* @exception Exception if something goes wrong
*/
public void buildDecList(Instances data, boolean leaf) throws Exception {
Instances [] localInstances,localPruneInstances;
int index,ind;
int i,j;
double sumOfWeights;
NoSplit noSplit;
m_train = null;
m_test = null;
m_isLeaf = false;
m_isEmpty = false;
m_sons = null;
indeX = 0;
sumOfWeights = data.sumOfWeights();
noSplit = new NoSplit (new Distribution((Instances)data));
if (leaf)
m_localModel = noSplit;
else
m_localModel = m_toSelectModel.selectModel(data);
if (m_localModel.numSubsets() > 1) {
localInstances = m_localModel.split(data);
data = null;
m_sons = new ClassifierDecList [m_localModel.numSubsets()];
i = 0;
do {
i++;
ind = chooseIndex();
if (ind == -1) {
for (j = 0; j < m_sons.length; j++)
if (m_sons[j] == null)
m_sons[j] = getNewDecList(localInstances[j],true);
if (i < 2) {
m_localModel = noSplit;
m_isLeaf = true;
m_sons = null;
if (Utils.eq(sumOfWeights,0))
m_isEmpty = true;
return;
}
ind = 0;
break;
} else
m_sons[ind] = getNewDecList(localInstances[ind],false);
} while ((i < m_sons.length) && (m_sons[ind].m_isLeaf));
// Choose rule
indeX = chooseLastIndex();
}else{
m_isLeaf = true;
if (Utils.eq(sumOfWeights, 0))
m_isEmpty = true;
}
}
/**
* Classifies an instance.
*
* @exception Exception if something goes wrong
*/
public double classifyInstance(Instance instance)
throws Exception {
double maxProb = -1;
double currentProb;
int maxIndex = 0;
int j;
for (j = 0; j < instance.numClasses();
j++){
currentProb = getProbs(j,instance,1);
if (Utils.gr(currentProb,maxProb)){
maxIndex = j;
maxProb = currentProb;
}
}
if (Utils.eq(maxProb,0))
return -1.0;
else
return (double)maxIndex;
}
/**
* Returns class probabilities for a weighted instance.
*
* @exception Exception if something goes wrong
*/
public final double [] distributionForInstance(Instance instance)
throws Exception {
double [] doubles =
new double[instance.numClasses()];
for (int i = 0; i < doubles.length; i++)
doubles[i] = getProbs(i,instance,1);
return doubles;
}
/**
* Returns the weight a rule assigns to an instance.
*
* @exception Exception if something goes wrong
*/
public double weight(Instance instance) throws Exception {
int subset;
if (m_isLeaf)
return 1;
subset = m_localModel.whichSubset(instance);
if (subset == -1)
return (m_localModel.weights(instance))[indeX]*
m_sons[indeX].weight(instance);
if (subset == indeX)
return m_sons[indeX].weight(instance);
return 0;
}
/**
* Cleanup in order to save memory.
*/
public final void cleanup(Instances justHeaderInfo) {
m_train = justHeaderInfo;
m_test = null;
if (!m_isLeaf)
for (int i = 0; i < m_sons.length; i++)
if (m_sons[i] != null)
m_sons[i].cleanup(justHeaderInfo);
}
/**
* Prints rules.
*/
public String toString(){
try {
StringBuffer text;
text = new StringBuffer();
if (m_isLeaf){
text.append(": ");
text.append(m_localModel.dumpLabel(0,m_train)+"\n");
}else{
dumpDecList(text);
//dumpTree(0,text);
}
return text.toString();
} catch (Exception e) {
return "Can't print rule.";
}
}
/**
* Returns a newly created tree.
*
* @exception Exception if something goes wrong
*/
protected ClassifierDecList getNewDecList(Instances train, boolean leaf)
throws Exception {
ClassifierDecList newDecList = new ClassifierDecList(m_toSelectModel,
m_minNumObj);
newDecList.buildDecList(train,leaf);
return newDecList;
}
/**
* Method for choosing a subset to expand.
*/
public final int chooseIndex() {
int minIndex = -1;
double estimated, min = Double.MAX_VALUE;
int i, j;
for (i = 0; i < m_sons.length; i++)
if (son(i) == null) {
if (Utils.sm(localModel().distribution().perBag(i),
(double)m_minNumObj))
estimated = Double.MAX_VALUE;
else{
estimated = 0;
for (j = 0; j < localModel().distribution().numClasses(); j++)
estimated -= m_splitCrit.logFunc(localModel().distribution().
perClassPerBag(i,j));
estimated += m_splitCrit.logFunc(localModel().distribution().
perBag(i));
estimated /= localModel().distribution().perBag(i);
}
if (Utils.smOrEq(estimated,0))
return i;
if (Utils.sm(estimated,min)) {
min = estimated;
minIndex = i;
}
}
return minIndex;
}
/**
* Choose last index (ie. choose rule).
*/
public final int chooseLastIndex() {
int minIndex = 0;
double estimated, min = Double.MAX_VALUE;
if (!m_isLeaf)
for (int i = 0; i < m_sons.length; i++)
if (son(i) != null) {
if (Utils.grOrEq(localModel().distribution().perBag(i),
(double)m_minNumObj)) {
estimated = son(i).getSizeOfBranch();
if (Utils.sm(estimated,min)) {
min = estimated;
minIndex = i;
}
}
}
return minIndex;
}
/**
* Returns the number of instances covered by a branch
*/
protected double getSizeOfBranch() {
if (m_isLeaf) {
return -localModel().distribution().total();
} else
return son(indeX).getSizeOfBranch();
}
/**
* Help method for printing tree structure.
*/
private void dumpDecList(StringBuffer text) throws Exception {
text.append(m_localModel.leftSide(m_train));
text.append(m_localModel.rightSide(indeX, m_train));
if (m_sons[indeX].m_isLeaf){
text.append(": ");
text.append(m_localModel.dumpLabel(indeX,m_train)+"\n");
}else{
text.append(" AND\n");
m_sons[indeX].dumpDecList(text);
}
}
/**
* Dumps the partial tree (only used for debugging)
*
* @exception Exception Exception if something goes wrong
*/
private void dumpTree(int depth,StringBuffer text)
throws Exception {
int i,j;
for (i=0;i<m_sons.length;i++){
text.append("\n");;
for (j=0;j<depth;j++)
text.append("| ");
text.append(m_localModel.leftSide(m_train));
text.append(m_localModel.rightSide(i, m_train));
if (m_sons[i] == null)
text.append("null");
else if (m_sons[i].m_isLeaf){
text.append(": ");
text.append(m_localModel.dumpLabel(i,m_train));
}else
m_sons[i].dumpTree(depth+1,text);
}
}
/**
* Help method for computing class probabilities of
* a given instance.
*
* @exception Exception Exception if something goes wrong
*/
private double getProbs(int classIndex,Instance instance,
double weight) throws Exception {
double [] weights;
int treeIndex;
if (m_isLeaf) {
return weight * localModel().classProb(classIndex, instance, -1);
} else {
treeIndex = localModel().whichSubset(instance);
if (treeIndex == -1) {
weights = localModel().weights(instance);
return son(indeX).getProbs(classIndex, instance,
weights[indeX] * weight);
}else{
if (treeIndex == indeX) {
return son(indeX).getProbs(classIndex, instance, weight);
} else {
return 0;
}
}
}
}
/**
* Method just exists to make program easier to read.
*/
protected ClassifierSplitModel localModel(){
return (ClassifierSplitModel)m_localModel;
}
/**
* Method just exists to make program easier to read.
*/
protected ClassifierDecList son(int index){
return m_sons[index];
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 1.13 $");
}
}