Package weka.associations

Class ItemSet

  • All Implemented Interfaces:
    java.io.Serializable, RevisionHandler
    Direct Known Subclasses:
    AprioriItemSet, LabeledItemSet
    public class ItemSet
extends java.lang.Object
implements java.io.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: 13477 $
    Author:
    Eibe Frank (eibe@cs.waikato.ac.nz)
    See Also:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      ItemSet​(int totalTrans)
      Constructor
      ItemSet​(int[] array)
      Contsructor
      ItemSet​(int totalTrans, int[] array)
      Constructor

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean containedBy​(Instance instance)
      Checks if an instance contains an item set.
      boolean containedByTreatZeroAsMissing​(Instance instance)
      Checks if an instance contains an item set.
      int counter()
      Gets the counter
      static java.util.ArrayList<java.lang.Object> deleteItemSets​(java.util.ArrayList<java.lang.Object> itemSets, int minSupport, int maxSupport)
      Deletes all item sets that don't have minimum support.
      boolean equals​(java.lang.Object itemSet)
      Tests if two item sets are equal.
      static java.util.Hashtable<ItemSet,​java.lang.Integer> getHashtable​(java.util.ArrayList<java.lang.Object> itemSets, int initialSize)
      Return a hashtable filled with the given item sets.
      int[] getItems()
      Get the item array
      java.lang.String getRevision()
      Returns the revision string.
      int getTotalTransactions()
      Get the total number of transactions
      int hashCode()
      Produces a hash code for a item set.
      int itemAt​(int k)
      Gest the index of the value of the specified attribute
      int[] items()
      Gest the item set as an int array
      static java.util.ArrayList<java.lang.Object> mergeAllItemSets​(java.util.ArrayList<java.lang.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.
      static java.util.ArrayList<java.lang.Object> pruneItemSets​(java.util.ArrayList<java.lang.Object> toPrune, java.util.Hashtable<ItemSet,​java.lang.Integer> kMinusOne)
      Prunes a set of (k)-item sets using the given (k-1)-item sets.
      static void pruneRules​(java.util.ArrayList<java.lang.Object>[] rules, double minConfidence)
      Prunes a set of rules.
      void setCounter​(int count)
      Sets the counter
      void setItem​(int[] items)
      Sets an item sets
      void setItemAt​(int value, int k)
      Sets the index of an attribute value
      static java.util.ArrayList<java.lang.Object> singletons​(Instances instances)
      Converts the header info of the given set of instances into a set of item sets (singletons).
      int support()
      Outputs the support for an item set.
      java.lang.String toString​(Instances instances)
      Returns the contents of an item set as a string.
      java.lang.String toString​(Instances instances, char outerDelim, char innerDelim)
      Returns the contents of an item set as a delimited string.
      void upDateCounter​(Instance instance)
      Updates counter of item set with respect to given transaction.
      static void upDateCounters​(java.util.ArrayList<java.lang.Object> itemSets, Instances instances)
      Updates counters for a set of item sets and a set of instances.
      static void upDateCountersTreatZeroAsMissing​(java.util.ArrayList<java.lang.Object> itemSets, Instances instances)
      Updates counters for a set of item sets and a set of instances.
      void updateCounterTreatZeroAsMissing​(Instance instance)
      Updates counter of item set with respect to given transaction.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • 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 Detail

      • 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 java.util.ArrayList<java.lang.Object> deleteItemSets​(java.util.ArrayList<java.lang.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​(java.lang.Object itemSet)
        Tests if two item sets are equal.
        Overrides:
        equals in class java.lang.Object
        Parameters:
        itemSet - another item set
        Returns:
        true if this item set contains the same items as the given one

      • getHashtable

        public static java.util.Hashtable<ItemSet,​java.lang.Integer> getHashtable​(java.util.ArrayList<java.lang.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 java.lang.Object
        Returns:
        a hash code for a set of items

      • mergeAllItemSets

        public static java.util.ArrayList<java.lang.Object> mergeAllItemSets​(java.util.ArrayList<java.lang.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 java.util.ArrayList<java.lang.Object> pruneItemSets​(java.util.ArrayList<java.lang.Object> toPrune,
                                                                  java.util.Hashtable<ItemSet,​java.lang.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​(java.util.ArrayList<java.lang.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 java.util.ArrayList<java.lang.Object> singletons​(Instances instances)
                                                        throws java.lang.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:
        java.lang.Exception - if singletons can't be generated successfully

      • support

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

      • toString

        public java.lang.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 java.lang.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​(java.util.ArrayList<java.lang.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​(java.util.ArrayList<java.lang.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 java.lang.String getRevision()
        Returns the revision string.
        Specified by:
        getRevision in interface RevisionHandler
        Returns:
        the revision