weka.associations

## Class ItemSet

- java.lang.Object
- - weka.associations.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: 12014 $
  Author:
    Eibe Frank (eibe@cs.waikato.ac.nz)
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and 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 and 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.
    `java.lang.String` | `getRevision()` Returns the revision string.
    `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

    - #### getRevision

          public java.lang.String getRevision()

      Returns the revision string.
      Specified by:
        `getRevision` in interface `RevisionHandler`
      Returns:
        the revision