Package weka.associations

Class ItemSet

java.lang.Object
weka.associations.ItemSet
All Implemented Interfaces:
Serializable, RevisionHandler
Direct Known Subclasses:
AprioriItemSet, LabeledItemSet
public class ItemSet extends Object implements Serializable, RevisionHandler
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.
Version:
$Revision: 13476 $
Author:
Eibe Frank (eibe@cs.waikato.ac.nz)
See Also:

  • Constructor Details

    • ItemSet

      public ItemSet(int totalTrans)
      Constructor
      Parameters:
      totalTrans - the total number of transactions in the data

    • ItemSet

      public ItemSet(int totalTrans, int[] array)
      Constructor
      Parameters:
      totalTrans - the total number of transactions in the data
      array - the attribute values encoded in an int array

    • ItemSet

      public ItemSet(int[] array)
      Contsructor
      Parameters:
      array - the item set represented as an int array

  • Method Details

    • containedByTreatZeroAsMissing

      public boolean containedByTreatZeroAsMissing(Instance instance)
      Checks if an instance contains an item set.
      Parameters:
      instance - the instance to be tested
      Returns:
      true if the given instance contains this item set

    • containedBy

      public boolean containedBy(Instance instance)
      Checks if an instance contains an item set.
      Parameters:
      instance - the instance to be tested
      Returns:
      true if the given instance contains this item set

    • deleteItemSets

      public static ArrayList<Object> deleteItemSets(ArrayList<Object> itemSets, int minSupport, int maxSupport)
      Deletes all item sets that don't have minimum support.
      Parameters:
      maxSupport - the maximum support
      itemSets - the set of item sets to be pruned
      minSupport - the minimum number of transactions to be covered
      Returns:
      the reduced set of item sets

    • equals

      public boolean equals(Object itemSet)
      Tests if two item sets are equal.
      Overrides:
      equals in class Object
      Parameters:
      itemSet - another item set
      Returns:
      true if this item set contains the same items as the given one

    • getHashtable

      public static Hashtable<ItemSet,Integer> getHashtable(ArrayList<Object> itemSets, int initialSize)
      Return a hashtable filled with the given item sets.
      Parameters:
      itemSets - the set of item sets to be used for filling the hash table
      initialSize - the initial size of the hashtable
      Returns:
      the generated hashtable

    • hashCode

      public int hashCode()
      Produces a hash code for a item set.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code for a set of items

    • mergeAllItemSets

      public static ArrayList<Object> mergeAllItemSets(ArrayList<Object> itemSets, int size, int totalTrans)
      Merges all item sets in the set of (k-1)-item sets to create the (k)-item sets and updates the counters.
      Parameters:
      totalTrans - thetotal number of transactions
      itemSets - the set of (k-1)-item sets
      size - the value of (k-1)
      Returns:
      the generated (k)-item sets

    • pruneItemSets

      public static ArrayList<Object> pruneItemSets(ArrayList<Object> toPrune, Hashtable<ItemSet,Integer> kMinusOne)
      Prunes a set of (k)-item sets using the given (k-1)-item sets.
      Parameters:
      toPrune - the set of (k)-item sets to be pruned
      kMinusOne - the (k-1)-item sets to be used for pruning
      Returns:
      the pruned set of item sets

    • pruneRules

      public static void pruneRules(ArrayList<Object>[] rules, double minConfidence)
      Prunes a set of rules.
      Parameters:
      rules - a two-dimensional array of lists of item sets. The first list of item sets contains the premises, the second one the consequences.
      minConfidence - the minimum confidence the rules have to have

    • singletons

      public static ArrayList<Object> singletons(Instances instances) throws Exception
      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.
      Parameters:
      instances - the set of instances whose header info is to be used
      Returns:
      a set of item sets, each containing a single item
      Throws:
      Exception - if singletons can't be generated successfully

    • support

      public int support()
      Outputs the support for an item set.
      Returns:
      the support

    • toString

      public String toString(Instances instances)
      Returns the contents of an item set as a string.
      Parameters:
      instances - contains the relevant header information
      Returns:
      string describing the item set

    • toString

      public String toString(Instances instances, char outerDelim, char innerDelim)
      Returns the contents of an item set as a delimited string.
      Parameters:
      instances - contains the relevant header information
      outerDelim - the outer delimiter
      innerDelim - the inner delimiter
      Returns:
      string describing the item set

    • upDateCounter

      public void upDateCounter(Instance instance)
      Updates counter of item set with respect to given transaction.
      Parameters:
      instance - the instance to be used for ubdating the counter

    • updateCounterTreatZeroAsMissing

      public void updateCounterTreatZeroAsMissing(Instance instance)
      Updates counter of item set with respect to given transaction.
      Parameters:
      instance - the instance to be used for ubdating the counter

    • upDateCounters

      public static void upDateCounters(ArrayList<Object> itemSets, Instances instances)
      Updates counters for a set of item sets and a set of instances.
      Parameters:
      itemSets - the set of item sets which are to be updated
      instances - the instances to be used for updating the counters

    • upDateCountersTreatZeroAsMissing

      public static void upDateCountersTreatZeroAsMissing(ArrayList<Object> itemSets, Instances instances)
      Updates counters for a set of item sets and a set of instances.
      Parameters:
      itemSets - the set of item sets which are to be updated
      instances - the instances to be used for updating the counters

    • counter

      public int counter()
      Gets the counter
      Returns:
      the counter

    • items

      public int[] items()
      Gest the item set as an int array
      Returns:
      int array represneting an item set

    • itemAt

      public int itemAt(int k)
      Gest the index of the value of the specified attribute
      Parameters:
      k - the attribute index
      Returns:
      the index of the attribute value

    • setCounter

      public void setCounter(int count)
      Sets the counter
      Parameters:
      count - the counter

    • setItem

      public void setItem(int[] items)
      Sets an item sets
      Parameters:
      items - an int array representing an item set

    • setItemAt

      public void setItemAt(int value, int k)
      Sets the index of an attribute value
      Parameters:
      value - the inex of the attribute value
      k - the index of the attribute

    • getItems

      public int[] getItems()
      Get the item array
      Returns:
      the item array

    • getTotalTransactions

      public int getTotalTransactions()
      Get the total number of transactions
      Returns:
      the total number of transactions

    • getRevision

      public String getRevision()
      Returns the revision string.
      Specified by:
      getRevision in interface RevisionHandler
      Returns:
      the revision