org.apache.spark.mllib.fpm

Class PrefixSpan

Object

org.apache.spark.mllib.fpm.PrefixSpan

All Implemented Interfaces:

java.io.Serializable, Logging

public class PrefixSpan
extends Object
implements Logging, scala.Serializable

A parallel PrefixSpan algorithm to mine frequent sequential patterns. The PrefixSpan algorithm is described in J. Pei, et al., PrefixSpan: Mining Sequential Patterns Efficiently by Prefix-Projected Pattern Growth (see here).

param: minSupport the minimal support level of the sequential pattern, any pattern that appears more than (minSupport * size-of-the-dataset) times will be output param: maxPatternLength the maximal length of the sequential pattern param: maxLocalProjDBSize The maximum number of items (including delimiters used in the internal storage format) allowed in a projected database before local processing. If a projected database exceeds this size, another iteration of distributed prefix growth is run.

See Also:

Sequential Pattern Mining (Wikipedia), Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PrefixSpan.FreqSequence<Item> Represents a frequent sequence.
static class	PrefixSpan.Postfix$
static class	PrefixSpan.Prefix$

Constructor Summary

Constructors

Constructor and Description
PrefixSpan() Constructs a default instance with default parameters {minSupport: 0.1, maxPatternLength: 10, maxLocalProjDBSize: 32000000L}.

Method Summary

Modifier and Type	Method and Description
long	getMaxLocalProjDBSize() Gets the maximum number of items allowed in a projected database before local processing.
int	getMaxPatternLength() Gets the maximal pattern length (i.e.
double	getMinSupport() Get the minimal support (i.e.
<Item,Itemset extends Iterable<Item>,Sequence extends Iterable<Itemset>> PrefixSpanModel<Item>	run(JavaRDD<Sequence> data) A Java-friendly version of run() that reads sequences from a JavaRDD and returns frequent sequences in a PrefixSpanModel.
<Item> PrefixSpanModel<Item>	run(RDD<Object[]> data, scala.reflect.ClassTag<Item> evidence$1) Finds the complete set of frequent sequential patterns in the input sequences of itemsets.
PrefixSpan	setMaxLocalProjDBSize(long maxLocalProjDBSize) Sets the maximum number of items (including delimiters used in the internal storage format) allowed in a projected database before local processing (default: 32000000L).
PrefixSpan	setMaxPatternLength(int maxPatternLength) Sets maximal pattern length (default: 10).
PrefixSpan	setMinSupport(double minSupport) Sets the minimal support level (default: 0.1).

Methods inherited from class Object

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

Methods inherited from interface org.apache.spark.internal.Logging

initializeLogging, initializeLogIfNecessary, initializeLogIfNecessary, isTraceEnabled, log_, log, logDebug, logDebug, logError, logError, logInfo, logInfo, logName, logTrace, logTrace, logWarning, logWarning

Constructor Detail

PrefixSpan

public PrefixSpan()

Constructs a default instance with default parameters {minSupport: 0.1, maxPatternLength: 10, maxLocalProjDBSize: 32000000L}.

Method Detail

getMinSupport

public double getMinSupport()

Get the minimal support (i.e. the frequency of occurrence before a pattern is considered frequent).

Returns:

(undocumented)

setMinSupport

public PrefixSpan setMinSupport(double minSupport)

Sets the minimal support level (default: 0.1).

Parameters:

minSupport - (undocumented)

Returns:

(undocumented)

getMaxPatternLength

public int getMaxPatternLength()

Gets the maximal pattern length (i.e. the length of the longest sequential pattern to consider.

Returns:

(undocumented)

setMaxPatternLength

public PrefixSpan setMaxPatternLength(int maxPatternLength)

Sets maximal pattern length (default: 10).

Parameters:

maxPatternLength - (undocumented)

Returns:

(undocumented)

getMaxLocalProjDBSize

public long getMaxLocalProjDBSize()

Gets the maximum number of items allowed in a projected database before local processing.

Returns:

(undocumented)

setMaxLocalProjDBSize

public PrefixSpan setMaxLocalProjDBSize(long maxLocalProjDBSize)

Sets the maximum number of items (including delimiters used in the internal storage format) allowed in a projected database before local processing (default: 32000000L).

Parameters:

maxLocalProjDBSize - (undocumented)

Returns:

(undocumented)

run

public <Item> PrefixSpanModel<Item> run(RDD<Object[]> data,
                                        scala.reflect.ClassTag<Item> evidence$1)

Finds the complete set of frequent sequential patterns in the input sequences of itemsets.

Parameters:

data - sequences of itemsets.

evidence$1 - (undocumented)

Returns:

a PrefixSpanModel that contains the frequent patterns

run

public <Item,Itemset extends Iterable<Item>,Sequence extends Iterable<Itemset>> PrefixSpanModel<Item> run(JavaRDD<Sequence> data)

A Java-friendly version of run() that reads sequences from a JavaRDD and returns frequent sequences in a PrefixSpanModel.

Parameters:

data - ordered sequences of itemsets stored as Java Iterable of Iterables

Returns:

a PrefixSpanModel that contains the frequent sequential patterns