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The Waikato Environment for Knowledge Analysis (WEKA), a machine learning workbench. This is the stable version. Apart from bugfixes, this version does not receive any other updates.

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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 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 .
 */

/*
 *    ItemSet.java
 *    Copyright (C) 1999-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.associations;

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

import weka.core.Instance;
import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import weka.core.WekaEnumeration;

/**
 * Class for storing a set of items. Item sets are stored in a lexicographic
 * order, which is determined by the header information of the set of instances
 * used for generating the set of items. All methods in this class assume that
 * item sets are stored in lexicographic order. The class provides the general
 * methods used for item sets in class - and standard association rule mining.
 * 
 * @author Eibe Frank ([email protected])
 * @version $Revision: 12014 $
 */
public class ItemSet implements Serializable, RevisionHandler {

  /** for serialization */
  private static final long serialVersionUID = 2724000045282835791L;

  /** The items stored as an array of of ints. */
  protected int[] m_items;

  /** Counter for how many transactions contain this item set. */
  protected int m_counter;

  /**
   * Holds support of consequence only in the case where this ItemSet is
   * a consequence of a rule (as m_counter in this case actually holds the
   * support of the rule as a whole, i.e. premise and consequence)
   */
  protected int m_secondaryCounter;

  /** The total number of transactions */
  protected int m_totalTransactions;

  /**
   * Constructor
   * 
   * @param totalTrans the total number of transactions in the data
   */
  public ItemSet(int totalTrans) {
    m_totalTransactions = totalTrans;
  }

  /**
   * Constructor
   * 
   * @param totalTrans the total number of transactions in the data
   * @param array the attribute values encoded in an int array
   */
  public ItemSet(int totalTrans, int[] array) {

    m_totalTransactions = totalTrans;
    m_items = array;
    m_counter = 1;
  }

  /**
   * Contsructor
   * 
   * @param array the item set represented as an int array
   */
  public ItemSet(int[] array) {

    m_items = array;
    m_counter = 0;
  }

  /**
   * Checks if an instance contains an item set.
   * 
   * @param instance the instance to be tested
   * @return true if the given instance contains this item set
   */
  public boolean containedByTreatZeroAsMissing(Instance instance) {

    if (instance instanceof weka.core.SparseInstance) {
      int numInstVals = instance.numValues();
      int numItemSetVals = m_items.length;

      for (int p1 = 0, p2 = 0; p1 < numInstVals || p2 < numItemSetVals;) {
        int instIndex = Integer.MAX_VALUE;
        if (p1 < numInstVals) {
          instIndex = instance.index(p1);
        }
        int itemIndex = p2;

        if (m_items[itemIndex] > -1) {
          if (itemIndex != instIndex) {
            return false;
          } else {
            if (instance.isMissingSparse(p1)) {
              return false;
            }
            if (m_items[itemIndex] != (int) instance.valueSparse(p1)) {
              return false;
            }
          }

          p1++;
          p2++;
        } else {
          if (itemIndex < instIndex) {
            p2++;
          } else if (itemIndex == instIndex) {
            p2++;
            p1++;
          }
        }
      }
    } else {
      for (int i = 0; i < instance.numAttributes(); i++) {
        if (m_items[i] > -1) {
          if (instance.isMissing(i) || (int) instance.value(i) == 0) {
            return false;
          }
          if (m_items[i] != (int) instance.value(i)) {
            return false;
          }
        }
      }
    }

    return true;
  }

  /**
   * Checks if an instance contains an item set.
   * 
   * @param instance the instance to be tested
   * @return true if the given instance contains this item set
   */
  public boolean containedBy(Instance instance) {
    for (int i = 0; i < instance.numAttributes(); i++) {
      if (m_items[i] > -1) {
        if (instance.isMissing(i)) {
          return false;
        }
        if (m_items[i] != (int) instance.value(i)) {
          return false;
        }
      }
    }

    return true;
  }

  /**
   * Deletes all item sets that don't have minimum support.
   * 
   * @return the reduced set of item sets
   * @param maxSupport the maximum support
   * @param itemSets the set of item sets to be pruned
   * @param minSupport the minimum number of transactions to be covered
   */
  public static ArrayList deleteItemSets(ArrayList itemSets,
    int minSupport, int maxSupport) {

    ArrayList newVector = new ArrayList(itemSets.size());

    for (int i = 0; i < itemSets.size(); i++) {
      ItemSet current = (ItemSet) itemSets.get(i);
      if ((current.m_counter >= minSupport)
        && (current.m_counter <= maxSupport)) {
        newVector.add(current);
      }
    }
    return newVector;
  }

  /**
   * Tests if two item sets are equal.
   * 
   * @param itemSet another item set
   * @return true if this item set contains the same items as the given one
   */
  @Override
  public boolean equals(Object itemSet) {

    if ((itemSet == null) || !(itemSet.getClass().equals(this.getClass()))) {
      return false;
    }
    if (m_items.length != ((ItemSet) itemSet).m_items.length) {
      return false;
    }
    for (int i = 0; i < m_items.length; i++) {
      if (m_items[i] != ((ItemSet) itemSet).m_items[i]) {
        return false;
      }
    }
    return true;
  }

  /**
   * Return a hashtable filled with the given item sets.
   * 
   * @param itemSets the set of item sets to be used for filling the hash table
   * @param initialSize the initial size of the hashtable
   * @return the generated hashtable
   */
  public static Hashtable getHashtable(
    ArrayList itemSets, int initialSize) {

    Hashtable hashtable = new Hashtable(
      initialSize);

    for (int i = 0; i < itemSets.size(); i++) {
      ItemSet current = (ItemSet) itemSets.get(i);
      hashtable.put(current, new Integer(current.m_counter));
    }
    return hashtable;
  }

  /**
   * Produces a hash code for a item set.
   * 
   * @return a hash code for a set of items
   */
  @Override
  public int hashCode() {

    long result = 0;

    for (int i = m_items.length - 1; i >= 0; i--) {
      result += (i * m_items[i]);
    }
    return (int) result;
  }

  /**
   * Merges all item sets in the set of (k-1)-item sets to create the (k)-item
   * sets and updates the counters.
   * 
   * @return the generated (k)-item sets
   * @param totalTrans thetotal number of transactions
   * @param itemSets the set of (k-1)-item sets
   * @param size the value of (k-1)
   */
  public static ArrayList mergeAllItemSets(ArrayList itemSets,
    int size, int totalTrans) {

    ArrayList newVector = new ArrayList();
    ItemSet result;
    int numFound, k;

    for (int i = 0; i < itemSets.size(); i++) {
      ItemSet first = (ItemSet) itemSets.get(i);
      out: for (int j = i + 1; j < itemSets.size(); j++) {
        ItemSet second = (ItemSet) itemSets.get(j);
        result = new ItemSet(totalTrans);
        result.m_items = new int[first.m_items.length];

        // Find and copy common prefix of size 'size'
        numFound = 0;
        k = 0;
        while (numFound < size) {
          if (first.m_items[k] == second.m_items[k]) {
            if (first.m_items[k] != -1) {
              numFound++;
            }
            result.m_items[k] = first.m_items[k];
          } else {
            break out;
          }
          k++;
        }

        // Check difference
        while (k < first.m_items.length) {
          if ((first.m_items[k] != -1) && (second.m_items[k] != -1)) {
            break;
          } else {
            if (first.m_items[k] != -1) {
              result.m_items[k] = first.m_items[k];
            } else {
              result.m_items[k] = second.m_items[k];
            }
          }
          k++;
        }
        if (k == first.m_items.length) {
          result.m_counter = 0;

          newVector.add(result);
        }
      }
    }
    return newVector;
  }

  /**
   * Prunes a set of (k)-item sets using the given (k-1)-item sets.
   * 
   * @param toPrune the set of (k)-item sets to be pruned
   * @param kMinusOne the (k-1)-item sets to be used for pruning
   * @return the pruned set of item sets
   */
  public static ArrayList pruneItemSets(ArrayList toPrune,
    Hashtable kMinusOne) {

    ArrayList newVector = new ArrayList(toPrune.size());
    int help, j;

    for (int i = 0; i < toPrune.size(); i++) {
      ItemSet current = (ItemSet) toPrune.get(i);
      for (j = 0; j < current.m_items.length; j++) {
        if (current.m_items[j] != -1) {
          help = current.m_items[j];
          current.m_items[j] = -1;
          if (kMinusOne.get(current) == null) {
            current.m_items[j] = help;
            break;
          } else {
            current.m_items[j] = help;
          }
        }
      }
      if (j == current.m_items.length) {
        newVector.add(current);
      }
    }
    return newVector;
  }

  /**
   * Prunes a set of rules.
   * 
   * @param rules a two-dimensional array of lists of item sets. The first list
   *          of item sets contains the premises, the second one the
   *          consequences.
   * @param minConfidence the minimum confidence the rules have to have
   */
  public static void pruneRules(ArrayList[] rules, double minConfidence) {

    ArrayList newPremises = new ArrayList(rules[0].size()), newConsequences = new ArrayList(
      rules[1].size()), newConf = new ArrayList(rules[2].size());

    ArrayList newLift = null, newLev = null, newConv = null;
    if (rules.length > 3) {
      newLift = new ArrayList(rules[3].size());
      newLev = new ArrayList(rules[4].size());
      newConv = new ArrayList(rules[5].size());
    }

    for (int i = 0; i < rules[0].size(); i++) {
      if (!(((Double) rules[2].get(i)).doubleValue() < minConfidence)) {
        newPremises.add(rules[0].get(i));
        newConsequences.add(rules[1].get(i));
        newConf.add(rules[2].get(i));

        if (rules.length > 3) {
          newLift.add(rules[3].get(i));
          newLev.add(rules[4].get(i));
          newConv.add(rules[5].get(i));
        }
      }
    }
    rules[0] = newPremises;
    rules[1] = newConsequences;
    rules[2] = newConf;

    if (rules.length > 3) {
      rules[3] = newLift;
      rules[4] = newLev;
      rules[5] = newConv;
    }
  }

  /**
   * 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;

    for (int i = 0; i < instances.numAttributes(); i++) {
      if (instances.attribute(i).isNumeric()) {
        throw new Exception("Can't handle numeric attributes!");
      }
      for (int j = 0; j < instances.attribute(i).numValues(); j++) {
        current = new ItemSet(instances.numInstances());
        current.m_items = new int[instances.numAttributes()];
        for (int k = 0; k < instances.numAttributes(); k++) {
          current.m_items[k] = -1;
        }
        current.m_items[i] = j;

        setOfItemSets.add(current);
      }
    }
    return setOfItemSets;
  }

  /**
   * Outputs the support for an item set.
   * 
   * @return the support
   */
  public int support() {

    return m_counter;
  }

  /**
   * Returns the contents of an item set as a string.
   * 
   * @param instances contains the relevant header information
   * @return string describing the item set
   */
  public String toString(Instances instances) {

    StringBuffer text = new StringBuffer();

    for (int i = 0; i < instances.numAttributes(); i++) {
      if (m_items[i] != -1) {
        text.append(instances.attribute(i).name() + '=');
        text.append(instances.attribute(i).value(m_items[i]) + ' ');
      }
    }
    text.append(m_counter);
    return text.toString();
  }

  /**
   * Returns the contents of an item set as a delimited string.
   * 
   * @param instances contains the relevant header information
   * @param outerDelim the outer delimiter
   * @param innerDelim the inner delimiter
   * @return string describing the item set
   */
  public String toString(Instances instances, char outerDelim, char innerDelim) {

    StringBuffer text = new StringBuffer();

    for (int i = 0; i < instances.numAttributes(); i++) {
      if (m_items[i] != -1) {
        text.append(instances.attribute(i).name()).append('=')
          .append(instances.attribute(i).value(m_items[i])).append(innerDelim);
      }
    }

    int n = text.length();
    if (n > 0) {
      text.setCharAt(n - 1, outerDelim);
    } else {
      if (outerDelim != ' ' || innerDelim != ' ') {
        text.append(outerDelim);
      }
    }
    text.append(m_counter);
    return text.toString();
  }

  /**
   * Updates counter of item set with respect to given transaction.
   * 
   * @param instance the instance to be used for ubdating the counter
   */
  public void upDateCounter(Instance instance) {

    if (containedBy(instance)) {
      m_counter++;
    }
  }

  /**
   * Updates counter of item set with respect to given transaction.
   * 
   * @param instance the instance to be used for ubdating the counter
   */
  public void updateCounterTreatZeroAsMissing(Instance instance) {
    if (containedByTreatZeroAsMissing(instance)) {
      m_counter++;
    }
  }

  /**
   * Updates counters for a set of item sets and a set of instances.
   * 
   * @param itemSets the set of item sets which are to be updated
   * @param instances the instances to be used for updating the counters
   */
  public static void upDateCounters(ArrayList itemSets,
    Instances instances) {

    for (int i = 0; i < instances.numInstances(); i++) {
      Enumeration enu = new WekaEnumeration(itemSets);
      while (enu.hasMoreElements()) {
        ((ItemSet) enu.nextElement()).upDateCounter(instances.instance(i));
      }
    }
  }

  /**
   * Updates counters for a set of item sets and a set of instances.
   * 
   * @param itemSets the set of item sets which are to be updated
   * @param instances the instances to be used for updating the counters
   */
  public static void upDateCountersTreatZeroAsMissing(
    ArrayList itemSets, Instances instances) {
    for (int i = 0; i < instances.numInstances(); i++) {
      Enumeration enu = new WekaEnumeration(itemSets);
      while (enu.hasMoreElements()) {
        ((ItemSet) enu.nextElement()).updateCounterTreatZeroAsMissing(instances
          .instance(i));
      }
    }
  }

  /**
   * Gets the counter
   * 
   * @return the counter
   */
  public int counter() {

    return m_counter;
  }

  /**
   * Gest the item set as an int array
   * 
   * @return int array represneting an item set
   */
  public int[] items() {

    return m_items;
  }

  /**
   * Gest the index of the value of the specified attribute
   * 
   * @param k the attribute index
   * @return the index of the attribute value
   */
  public int itemAt(int k) {

    return m_items[k];
  }

  /**
   * Sets the counter
   * 
   * @param count the counter
   */
  public void setCounter(int count) {

    m_counter = count;
  }

  /**
   * Sets an item sets
   * 
   * @param items an int array representing an item set
   */
  public void setItem(int[] items) {

    m_items = items;
  }

  /**
   * Sets the index of an attribute value
   * 
   * @param value the inex of the attribute value
   * @param k the index of the attribute
   */
  public void setItemAt(int value, int k) {

    m_items[k] = value;
  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision: 12014 $");
  }
}
 















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