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    • weka.associations.CaRuleGeneration Maven / Gradle / Ivy

    /*
 *   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 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see .
 */

/*
 *    CaRuleGeneration.java
 *    Copyright (C) 2004 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.associations;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.TreeSet;

import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import weka.core.UnassignedClassException;

/**
 * Class implementing the rule generation procedure of the predictive apriori
 * algorithm for class association rules.
 * 
 * For association rules in gerneral the method is described in: T. Scheffer
 * (2001). Finding Association Rules That Trade Support Optimally against
 * Confidence. Proc of the 5th European Conf. on Principles and Practice of
 * Knowledge Discovery in Databases (PKDD'01), pp. 424-435. Freiburg, Germany:
 * Springer-Verlag.
 * 
    
 * 
 * The implementation follows the paper expect for adding a rule to the output
 * of the n best rules. A rule is added if: the expected predictive
 * accuracy of this rule is among the n best and it is not subsumed by a
 * rule with at least the same expected predictive accuracy (out of an
 * unpublished manuscript from T. Scheffer).
 * 
 * @author Stefan Mutter ([email protected])
 * @version $Revision: 10201 $
 */
public class CaRuleGeneration extends RuleGeneration implements Serializable,
  RevisionHandler {

  /** for serialization */
  private static final long serialVersionUID = 3065752149646517703L;

  /**
   * Constructor
   * 
   * @param itemSet the item set that forms the premise of the rule
   */
  public CaRuleGeneration(ItemSet itemSet) {
    super(itemSet);
  }

  /**
   * Generates all rules for an item set. The item set is the premise.
   * 
   * @param numRules the number of association rules the use wants to mine. This
   *          number equals the size n of the list of the best rules.
   * @param midPoints the mid points of the intervals
   * @param priors Hashtable that contains the prior probabilities
   * @param expectation the minimum value of the expected predictive accuracy
   *          that is needed to get into the list of the best rules
   * @param instances the instances for which association rules are generated
   * @param best the list of the n best rules. The list is implemented as
   *          a TreeSet
   * @param genTime the maximum time of generation
   * @return all the rules with minimum confidence for the given item set
   */
  @Override
  public TreeSet generateRules(int numRules, double[] midPoints,
    Hashtable priors, double expectation, Instances instances,
    TreeSet best, int genTime) {

    boolean redundant = false;
    ArrayList consequences = new ArrayList();
    ItemSet premise;
    RuleItem current = null;

    m_change = false;
    m_midPoints = midPoints;
    m_priors = priors;
    m_best = best;
    m_expectation = expectation;
    m_count = genTime;
    m_instances = instances;

    // create rule body
    premise = null;
    premise = new ItemSet(m_totalTransactions);
    int[] premiseItems = new int[m_items.length];
    System.arraycopy(m_items, 0, premiseItems, 0, m_items.length);
    premise.setItem(premiseItems);
    premise.setCounter(m_counter);

    consequences = singleConsequence(instances);

    // create n best rules
    do {
      if (premise == null || consequences.size() == 0) {
        return m_best;
      }
      m_minRuleCount = 1;
      while (expectation(m_minRuleCount, premise.counter(), m_midPoints,
        m_priors) <= m_expectation) {
        m_minRuleCount++;
        if (m_minRuleCount > premise.counter()) {
          return m_best;
        }
      }
      redundant = false;

      // create possible heads
      ArrayList allRuleItems = new ArrayList();
      int h = 0;
      while (h < consequences.size()) {
        RuleItem dummie = new RuleItem();
        m_count++;
        current = dummie.generateRuleItem(premise,
          (ItemSet) consequences.get(h), instances, m_count, m_minRuleCount,
          m_midPoints, m_priors);
        if (current != null) {
          allRuleItems.add(current);
        }
        h++;
      }

      // update best
      for (h = 0; h < allRuleItems.size(); h++) {
        current = (RuleItem) allRuleItems.get(h);
        if (m_best.size() < numRules) {
          m_change = true;
          redundant = removeRedundant(current);
        } else {
          m_expectation = (m_best.first()).accuracy();
          if (current.accuracy() > m_expectation) {
            m_best.remove(m_best.first());
            m_change = true;
            redundant = removeRedundant(current);
            m_expectation = (m_best.first()).accuracy();
            while (expectation(m_minRuleCount, (current.premise()).counter(),
              m_midPoints, m_priors) < m_expectation) {
              m_minRuleCount++;
              if (m_minRuleCount > (current.premise()).counter()) {
                break;
              }
            }
          }
        }
      }
    } while (redundant);
    return m_best;
  }

  /**
   * Methods that decides whether or not rule a subsumes rule b. The defintion
   * of subsumption is: Rule a subsumes rule b, if a subsumes b AND a has got
   * least the same expected predictive accuracy as b.
   * 
   * @param a an association rule stored as a RuleItem
   * @param b an association rule stored as a RuleItem
   * @return true if rule a subsumes rule b or false otherwise.
   */
  public static boolean aSubsumesB(RuleItem a, RuleItem b) {

    if (!a.consequence().equals(b.consequence())) {
      return false;
    }
    if (a.accuracy() < b.accuracy()) {
      return false;
    }
    for (int k = 0; k < ((a.premise()).items()).length; k++) {
      if ((a.premise()).itemAt(k) != (b.premise()).itemAt(k)) {
        if (((a.premise()).itemAt(k) != -1 && (b.premise()).itemAt(k) != -1)
          || (b.premise()).itemAt(k) == -1) {
          return false;
        }
      }
      /*
       * if(a.m_consequence.m_items[k] != b.m_consequence.m_items[k]){
       * if((a.m_consequence.m_items[k] != -1 && b.m_consequence.m_items[k] !=
       * -1) || a.m_consequence.m_items[k] == -1) return false; }
       */
    }
    return true;

  }

  /**
   * Converts the header info of the given set of instances into a set of item
   * sets (singletons). The ordering of values in the header file determines the
   * lexicographic order.
   * 
   * @param instances the set of instances whose header info is to be used
   * @return a set of item sets, each containing a single item
   * @exception Exception if singletons can't be generated successfully
   */
  public static ArrayList singletons(Instances instances)
    throws Exception {

    ArrayList setOfItemSets = new ArrayList();
    ItemSet current;

    if (instances.classIndex() == -1) {
      throw new UnassignedClassException("Class index is negative (not set)!");
    }
    instances.classAttribute();
    for (int i = 0; i < instances.numAttributes(); i++) {
      if (instances.attribute(i).isNumeric()) {
        throw new Exception("Can't handle numeric attributes!");
      }
      if (i != instances.classIndex()) {
        for (int j = 0; j < instances.attribute(i).numValues(); j++) {
          current = new ItemSet(instances.numInstances());
          int[] currentItems = new int[instances.numAttributes()];
          for (int k = 0; k < instances.numAttributes(); k++) {
            currentItems[k] = -1;
          }
          currentItems[i] = j;
          current.setItem(currentItems);
          setOfItemSets.add(current);
        }
      }
    }
    return setOfItemSets;
  }

  /**
   * generates a consequence of length 1 for a class association rule.
   * 
   * @param instances the instances under consideration
   * @return FastVector with consequences of length 1
   */
  public static ArrayList singleConsequence(Instances instances) {

    ItemSet consequence;
    ArrayList consequences = new ArrayList();

    for (int j = 0; j < (instances.classAttribute()).numValues(); j++) {
      consequence = new ItemSet(instances.numInstances());
      int[] consequenceItems = new int[instances.numAttributes()];
      consequence.setItem(consequenceItems);
      for (int k = 0; k < instances.numAttributes(); k++) {
        consequence.setItemAt(-1, k);
      }
      consequence.setItemAt(j, instances.classIndex());
      consequences.add(consequence);
    }
    return consequences;

  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision: 10201 $");
  }
}
    
    
    
    

    




    
    
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