de.lmu.ifi.dbs.elki.algorithm.itemsetmining

Class FPGrowth

java.lang.Object

de.lmu.ifi.dbs.elki.algorithm.AbstractAlgorithm<FrequentItemsetsResult>

de.lmu.ifi.dbs.elki.algorithm.itemsetmining.AbstractFrequentItemsetAlgorithm

de.lmu.ifi.dbs.elki.algorithm.itemsetmining.FPGrowth

All Implemented Interfaces:

Algorithm

@Reference(authors="J. Han, J. Pei, Y. Yin",
           title="Mining frequent patterns without candidate generation",
           booktitle="Proceedings of the 2000 ACM SIGMOD international conference on Management of data ",
           url="http://dx.doi.org/10.1145/342009.335372")
public class FPGrowth
extends AbstractFrequentItemsetAlgorithm

FP-Growth is an algorithm for mining the frequent itemsets by using a compressed representation of the database called FPGrowth.FPTree. FP-Growth first sorts items by the overall frequency, since having high frequent items appear first in the tree leads to a much smaller tree since frequent subsets will likely share the same path in the tree. FP-Growth is beneficial when you have a lot of (near-) duplicate transactions, and are using a not too high support threshold, as it only prunes single items, not item combinations. This implementation is in-memory only, and has not yet been carefully optimized. The worst case memory use probably is O(min(n*l,i^l)) where i is the number of items, l the average itemset length, and n the number of items. The worst case scenario is when every item is frequent, and every transaction is unique. The resulting tree will then be larger than the original data. Reference:

J. Han, J. Pei, Y. Yin
Mining frequent patterns without candidate generation
In proceedings of the 2000 ACM SIGMOD international conference on Management of data.

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FPGrowth.FPNode A single node of the FP tree.
static class	FPGrowth.FPTree FP-Tree data structure
static class	FPGrowth.Parameterizer Parameterization class.

Field Summary

Fields

Modifier and Type	Field and Description
private static Logging	LOG Class logger.
private static String	STAT Prefix for statistics.

Fields inherited from class de.lmu.ifi.dbs.elki.algorithm.itemsetmining.AbstractFrequentItemsetAlgorithm

maxlength, minlength

Constructor Summary

Constructors

Constructor and Description
FPGrowth(double minsupp, int minlength, int maxlength) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
private FPGrowth.FPTree	buildFPTree(Relation<BitVector> relation, int[] iidx, int items) Build the actual FP-tree structure.
private int[]	buildIndex(int[] counts, int[] positions, int minsupp) Build a forward map, item id (dimension) to frequency position
private int[]	countItemSupport(Relation<BitVector> relation, int dim) Count the support of each 1-item.
TypeInformation[]	getInputTypeRestriction() Get the input type restriction used for negotiating the data query.
protected Logging	getLogger() Get the (STATIC) logger for this class.
FrequentItemsetsResult	run(Database db, Relation<BitVector> relation) Run the FP-Growth algorithm

Methods inherited from class de.lmu.ifi.dbs.elki.algorithm.itemsetmining.AbstractFrequentItemsetAlgorithm

getMinimumSupport

Methods inherited from class de.lmu.ifi.dbs.elki.algorithm.AbstractAlgorithm

makeParameterDistanceFunction, run

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final Logging LOG

Class logger.

STAT

private static final String STAT

Prefix for statistics.

Constructor Detail

FPGrowth

public FPGrowth(double minsupp,
        int minlength,
        int maxlength)

Constructor.

Parameters:

minsupp - Minimum support (relative or absolute)

minlength - Minimum length

maxlength - Maximum length

Method Detail

run

public FrequentItemsetsResult run(Database db,
                         Relation<BitVector> relation)

Run the FP-Growth algorithm

Parameters:

db - Database to process

relation - Bit vector relation

Returns:

Frequent patterns found

countItemSupport

private int[] countItemSupport(Relation<BitVector> relation,
                     int dim)

Count the support of each 1-item.

Parameters:

relation - Data

dim - Maximum dimensionality

Returns:

Item counts

buildFPTree

private FPGrowth.FPTree buildFPTree(Relation<BitVector> relation,
                          int[] iidx,
                          int items)

Build the actual FP-tree structure.

Parameters:

relation - Data

iidx - Inverse index (dimension to item rank)

items - Number of items

Returns:

FP-tree

buildIndex

private int[] buildIndex(int[] counts,
               int[] positions,
               int minsupp)

Build a forward map, item id (dimension) to frequency position

Parameters:

counts - Item counts

positions - Position index (output)

minsupp - Minimum support

Returns:

Forward index

getInputTypeRestriction

public TypeInformation[] getInputTypeRestriction()

Description copied from class: AbstractAlgorithm

Get the input type restriction used for negotiating the data query.

Specified by:

getInputTypeRestriction in interface Algorithm

Specified by:

getInputTypeRestriction in class AbstractAlgorithm<FrequentItemsetsResult>

Returns:

Type restriction

getLogger

protected Logging getLogger()

Description copied from class: AbstractAlgorithm

Get the (STATIC) logger for this class.

Specified by:

getLogger in class AbstractAlgorithm<FrequentItemsetsResult>

Returns:

the static logger