distribution.java

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/*
 *    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.
 */

/*
 *    Distribution.java
 *    Copyright (C) 1999 Eibe Frank
 *
 */

package weka.classifiers.j48;

import java.io.*;
import java.util.*;
import weka.core.*;

/**
 * Class for handling a distribution of class values.
 *
 * @author Eibe Frank ([e-mail])
 * @version $Revision: 1.6 $
 */
public class Distribution implements Cloneable, Serializable {

  /** Weight of instances per class per bag. */
  private double m_perClassPerBag[][]; 

  /** Weight of instances per bag. */
  private double m_perBag[];           

  /** Weight of instances per class. */
  private double m_perClass[];         

  /** Total weight of instances. */
  private double totaL;            

  /**
   * Creates and initializes a new distribution.
   */
  public Distribution(int numBags,int numClasses) {

    int i;

    m_perClassPerBag = new double [numBags][0];
    m_perBag = new double [numBags];
    m_perClass = new double [numClasses];
    for (i=0;i<numBags;i++)
      m_perClassPerBag[i] = new double [numClasses];
    totaL = 0;
  }

  /**
   * Creates and initializes a new distribution using the given
   * array. WARNING: it just copies a reference to this array.
   */
  public Distribution(double [][] table) {

    int i, j;

    m_perClassPerBag = table;
    m_perBag = new double [table.length];
    m_perClass = new double [table[0].length];
    for (i = 0; i < table.length; i++) 
      for (j  = 0; j < table[i].length; j++) {
	m_perBag[i] += table[i][j];
	m_perClass[j] += table[i][j];
	totaL += table[i][j];
      }
  }

  /**
   * Creates a distribution with only one bag according
   * to instances in source.
   *
   * @exception Exception if something goes wrong
   */
  public Distribution(Instances source) throws Exception {
    
    m_perClassPerBag = new double [1][0];
    m_perBag = new double [1];
    totaL = 0;
    m_perClass = new double [source.numClasses()];
    m_perClassPerBag[0] = new double [source.numClasses()];
    Enumeration enum = source.enumerateInstances();
    while (enum.hasMoreElements())
      add(0,(Instance) enum.nextElement());
  }

  /**
   * Creates a distribution according to given instances and
   * split model.
   *
   * @exception Exception if something goes wrong
   */

  public Distribution(Instances source, 
		      ClassifierSplitModel modelToUse)
       throws Exception {

    int index;
    Instance instance;
    double[] weights;

    m_perClassPerBag = new double [modelToUse.numSubsets()][0];
    m_perBag = new double [modelToUse.numSubsets()];
    totaL = 0;
    m_perClass = new double [source.numClasses()];
    for (int i = 0; i < modelToUse.numSubsets(); i++)
      m_perClassPerBag[i] = new double [source.numClasses()];
    Enumeration enum = source.enumerateInstances();
    while (enum.hasMoreElements()) {
      instance = (Instance) enum.nextElement();
      index = modelToUse.whichSubset(instance);
      if (index != -1)
	add(index, instance);
      else {
	weights = modelToUse.weights(instance);
	addWeights(instance, weights);
      }
    }
  }

  /**
   * Creates distribution with only one bag by merging all
   * bags of given distribution.
   */
  public Distribution(Distribution toMerge) {

    totaL = toMerge.totaL;
    m_perClass = new double [toMerge.numClasses()];
    System.arraycopy(toMerge.m_perClass,0,m_perClass,0,toMerge.numClasses());
    m_perClassPerBag = new double [1] [0];
    m_perClassPerBag[0] = new double [toMerge.numClasses()];
    System.arraycopy(toMerge.m_perClass,0,m_perClassPerBag[0],0,
		     toMerge.numClasses());
    m_perBag = new double [1];
    m_perBag[0] = totaL;
  }

  /**
   * Creates distribution with two bags by merging all bags apart of
   * the indicated one.
   */
  public Distribution(Distribution toMerge, int index) {

    int i;

    totaL = toMerge.totaL;
    m_perClass = new double [toMerge.numClasses()];
    System.arraycopy(toMerge.m_perClass,0,m_perClass,0,toMerge.numClasses());
    m_perClassPerBag = new double [2] [0];
    m_perClassPerBag[0] = new double [toMerge.numClasses()];
    System.arraycopy(toMerge.m_perClassPerBag[index],0,m_perClassPerBag[0],0,
		     toMerge.numClasses());
    m_perClassPerBag[1] = new double [toMerge.numClasses()];
    for (i=0;i<toMerge.numClasses();i++)
      m_perClassPerBag[1][i] = toMerge.m_perClass[i]-m_perClassPerBag[0][i];
    m_perBag = new double [2];
    m_perBag[0] = toMerge.m_perBag[index];
    m_perBag[1] = totaL-m_perBag[0];
  }
  
  /**
   * Returns number of non-empty bags of distribution.
   */
  public final int actualNumBags() {
    
    int returnValue = 0;
    int i;

    for (i=0;i<m_perBag.length;i++)
      if (Utils.gr(m_perBag[i],0))
	returnValue++;
    
    return returnValue;
  }

  /**
   * Returns number of classes actually occuring in distribution.
   */
  public final int actualNumClasses() {

    int returnValue = 0;
    int i;

    for (i=0;i<m_perClass.length;i++)
      if (Utils.gr(m_perClass[i],0))
	returnValue++;
    
    return returnValue;
  }

  /**
   * Returns number of classes actually occuring in given bag.
   */
  public final int actualNumClasses(int bagIndex) {

    int returnValue = 0;
    int i;

    for (i=0;i<m_perClass.length;i++)
      if (Utils.gr(m_perClassPerBag[bagIndex][i],0))
	returnValue++;
    
    return returnValue;
  }

  /**
   * Adds given instance to given bag.
   *
   * @exception Exception if something goes wrong
   */
  public final void add(int bagIndex,Instance instance) 
       throws Exception {
    
    int classIndex;
    double weight;

    classIndex = (int)instance.classValue();
    weight = instance.weight();
    m_perClassPerBag[bagIndex][classIndex] = 
      m_perClassPerBag[bagIndex][classIndex]+weight;
    m_perBag[bagIndex] = m_perBag[bagIndex]+weight;
    m_perClass[classIndex] = m_perClass[classIndex]+weight;
    totaL = totaL+weight;
  }

  /**
   * Subtracts given instance from given bag.
   *
   * @exception Exception if something goes wrong
   */
  public final void sub(int bagIndex,Instance instance) 
       throws Exception {
    
    int classIndex;
    double weight;

    classIndex = (int)instance.classValue();
    weight = instance.weight();
    m_perClassPerBag[bagIndex][classIndex] = 
      m_perClassPerBag[bagIndex][classIndex]-weight;
    m_perBag[bagIndex] = m_perBag[bagIndex]-weight;
    m_perClass[classIndex] = m_perClass[classIndex]-weight;
    totaL = totaL-weight;
  }

  /**
   * Adds counts to given bag.
   */
  public final void add(int bagIndex, double[] counts) {
    
    double sum = Utils.sum(counts);

    for (int i = 0; i < counts.length; i++)
      m_perClassPerBag[bagIndex][i] += counts[i];
    m_perBag[bagIndex] = m_perBag[bagIndex]+sum;
    for (int i = 0; i < counts.length; i++)
      m_perClass[i] = m_perClass[i]+counts[i];
    totaL = totaL+sum;
  }

  /**
   * Adds all instances with unknown values for given attribute, weighted
   * according to frequency of instances in each bag.
   *
   * @exception Exception if something goes wrong
   */
  public final void addInstWithUnknown(Instances source,
				       int attIndex)
       throws Exception {

    double [] probs;
    double weight,newWeight;
    int classIndex;
    Instance instance;
    int j;

    probs = new double [m_perBag.length];
    for (j=0;j<m_perBag.length;j++) {
      if (Utils.eq(totaL, 0)) {
	probs[j] = 1.0 / probs.length;
      } else {
	probs[j] = m_perBag[j]/totaL;
      }
    }
    Enumeration enum = source.enumerateInstances();
    while (enum.hasMoreElements()) {
      instance = (Instance) enum.nextElement();
      if (instance.isMissing(attIndex)) {
	classIndex = (int)instance.classValue();
	weight = instance.weight();
	m_perClass[classIndex] = m_perClass[classIndex]+weight;
	totaL = totaL+weight;
	for (j = 0; j < m_perBag.length; j++) {
	  newWeight = probs[j]*weight;
	  m_perClassPerBag[j][classIndex] = m_perClassPerBag[j][classIndex]+
	    newWeight;
	  m_perBag[j] = m_perBag[j]+newWeight;
	}
      }
    }
  }

  /**
   * Adds all instances in given range to given bag.
   *
   * @exception Exception if something goes wrong
   */
  public final void addRange(int bagIndex,Instances source,
			     int startIndex, int lastPlusOne)
       throws Exception {

    double sumOfWeights = 0;
    int classIndex;
    Instance instance;
    int i;

    for (i = startIndex; i < lastPlusOne; i++) {
      instance = (Instance) source.instance(i);
      classIndex = (int)instance.classValue();
      sumOfWeights = sumOfWeights+instance.weight();
      m_perClassPerBag[bagIndex][classIndex] += instance.weight();
      m_perClass[classIndex] += instance.weight();
    }
    m_perBag[bagIndex] += sumOfWeights;
    totaL += sumOfWeights;
  }

  /**
   * Adds given instance to all bags weighting it according to given weights.
   *
   * @exception Exception if something goes wrong
   */
  public final void addWeights(Instance instance, 
			       double [] weights)
       throws Exception {

    int classIndex;
    int i;

    classIndex = (int)instance.classValue();
    for (i=0;i<m_perBag.length;i++) {
      double weight = instance.weight() * weights[i];
      m_perClassPerBag[i][classIndex] = m_perClassPerBag[i][classIndex] + weight;
      m_perBag[i] = m_perBag[i] + weight;
      m_perClass[classIndex] = m_perClass[classIndex] + weight;
      totaL = totaL + weight;
    }
  }

  /**
   * Checks if at least two bags contain a minimum number of instances.
   */
  public final boolean check(double minNoObj) {