ca.pfv.spmf.algorithms

Class ArraysAlgos

java.lang.Object

ca.pfv.spmf.algorithms.ArraysAlgos

public class ArraysAlgos
extends java.lang.Object

This class provides a set of basic methods that can be used with itemsets represented as arrays of integers. All the methods are static methods so that they can be used in any classes.

Field Summary

Fields

Modifier and Type	Field and Description
static java.util.Comparator<int[]>	comparatorItemsetSameSize A Comparator for comparing two itemsets having the same size using the lexical order.

Constructor Summary

Constructors

Constructor and Description
ArraysAlgos()

Method Summary

Modifier and Type	Method and Description
static boolean	allTheSameExceptLastItem(int[] itemset1, int[] itemset2) This method checks if this itemset is the same as another itemset except for the last item.
static int[]	cloneItemSetMinusAnItemset(int[] itemset, int[] itemsetToNotKeep) Make a copy of this itemset but exclude a set of items
static int[]	cloneItemSetMinusOneItem(int[] itemset, java.lang.Integer itemToRemove) Make a copy of this itemset but exclude a given item
static int[]	concatenate(int[] prefix, int[] suffix) Method to concatenate two arrays in a new array
static boolean	contains(int[] itemset, int item) Check if an a sorted list of integers contains an integer.
static boolean	containsLEX(int[] itemset, int item) This method checks if the item "item" is in the itemset.
static boolean	containsLEX(java.lang.Integer[] itemset, java.lang.Integer item, int maxItemInArray) This method checks if an item "item" is in the itemset "itemset".
static boolean	containsLEXPlus(int[] itemset, int item) This method checks if the item "item" is in the itemset.
static boolean	containsOrEquals(java.lang.Integer[] itemset1, java.lang.Integer[] itemset2) Check if an itemset contains another itemset.
static boolean	includedIn(int[] itemset1, int[] itemset2) Check if a sorted itemset is contained in another
static int[]	intersectTwoSortedArrays(int[] array1, int[] array2) This method performs the intersection of two sorted arrays of integers and return a new sorted array.
static int	sameAs(int[] itemset1, int[] itemsets2, int posRemoved) Method to compare two sorted list of integers and see if they are the same, while ignoring an item from the second list of integer.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

comparatorItemsetSameSize

public static java.util.Comparator<int[]> comparatorItemsetSameSize

A Comparator for comparing two itemsets having the same size using the lexical order.

Constructor Detail

ArraysAlgos

public ArraysAlgos()

Method Detail

cloneItemSetMinusOneItem

public static int[] cloneItemSetMinusOneItem(int[] itemset,
                                             java.lang.Integer itemToRemove)

Make a copy of this itemset but exclude a given item

Parameters:

itemToRemove - the given item

Returns:

the copy

cloneItemSetMinusAnItemset

public static int[] cloneItemSetMinusAnItemset(int[] itemset,
                                               int[] itemsetToNotKeep)

Make a copy of this itemset but exclude a set of items

Parameters:

itemsetToNotKeep - the set of items to be excluded

Returns:

the copy

allTheSameExceptLastItem

public static boolean allTheSameExceptLastItem(int[] itemset1,
                                               int[] itemset2)

This method checks if this itemset is the same as another itemset except for the last item. It assumes that both itemsets have the same length.

Parameters:

itemset1 - the first itemset

itemset2 - the second itemset

Returns:

true if they are the same except for the last item

concatenate

public static int[] concatenate(int[] prefix,
                                int[] suffix)

Method to concatenate two arrays in a new array

Parameters:

prefix - the first array

suffix - the second array

Returns:

the resulting array

intersectTwoSortedArrays

public static int[] intersectTwoSortedArrays(int[] array1,
                                             int[] array2)

This method performs the intersection of two sorted arrays of integers and return a new sorted array.

Parameters:

a - the first array

b - the second array

Returns:

the resulting sorted array

containsOrEquals

public static boolean containsOrEquals(java.lang.Integer[] itemset1,
                                       java.lang.Integer[] itemset2)

Check if an itemset contains another itemset. It assumes that itemsets are sorted according to the lexical order.

Parameters:

itemset1 - the first itemset

itemset2 - the second itemset

Returns:

true if the first itemset contains the second itemset

containsLEX

public static boolean containsLEX(java.lang.Integer[] itemset,
                                  java.lang.Integer item,
                                  int maxItemInArray)

This method checks if an item "item" is in the itemset "itemset". It assumes that items in the itemset are sorted in lexical order and that the largest item in the itemset is known.

Parameters:

itemset - an itemset

item - the item

maxItemInArray - the largest item in the itemset

Returns:

returnt true if the item appears in the itemset

sameAs

public static int sameAs(int[] itemset1,
                         int[] itemsets2,
                         int posRemoved)

Method to compare two sorted list of integers and see if they are the same, while ignoring an item from the second list of integer. This methods is used by some Apriori algorithms.

Parameters:

itemset1 - the first itemset

itemsets2 - the second itemset

posRemoved - the position of an item that should be ignored from "itemset2" to perform the comparison.

Returns:

0 if they are the same, 1 if itemset is larger according to lexical order, -1 if smaller.

includedIn

public static boolean includedIn(int[] itemset1,
                                 int[] itemset2)

Check if a sorted itemset is contained in another

Parameters:

itemset1 - the first itemset

itemset2 - the second itemset

Returns:

true if yes, otherwise false

containsLEXPlus

public static boolean containsLEXPlus(int[] itemset,
                                      int item)

This method checks if the item "item" is in the itemset. It asumes that items in the itemset are sorted in lexical order This version also checks that if the item "item" was added it would be the largest one according to the lexical order.

Parameters:

itemset - an itemset

item - the item

Returns:

return true if the above conditions are met, otherwise false

containsLEX

public static boolean containsLEX(int[] itemset,
                                  int item)

This method checks if the item "item" is in the itemset. It assumes that items in the itemset are sorted in lexical order

Parameters:

itemset - an itemset

item - the item

Returns:

return true if the item

contains

public static boolean contains(int[] itemset,
                               int item)

Check if an a sorted list of integers contains an integer.

Parameters:

itemset - the sorted list of integers

item - the integer

Returns:

true if the item appears in the list, false otherwise