PrefixSpan¶

class pyspark.ml.fpm.PrefixSpan(*, minSupport=0.1, maxPatternLength=10, maxLocalProjDBSize=32000000, sequenceCol='sequence')[source]¶

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). This class is not yet an Estimator/Transformer, use findFrequentSequentialPatterns() method to run the PrefixSpan algorithm.

New in version 2.4.0.

Notes

See Sequential Pattern Mining (Wikipedia)

Examples

>>> from pyspark.ml.fpm import PrefixSpan
>>> from pyspark.sql import Row
>>> df = sc.parallelize([Row(sequence=[[1, 2], [3]]),
...                      Row(sequence=[[1], [3, 2], [1, 2]]),
...                      Row(sequence=[[1, 2], [5]]),
...                      Row(sequence=[[6]])]).toDF()
>>> prefixSpan = PrefixSpan()
>>> prefixSpan.getMaxLocalProjDBSize()
32000000
>>> prefixSpan.getSequenceCol()
'sequence'
>>> prefixSpan.setMinSupport(0.5)
PrefixSpan...
>>> prefixSpan.setMaxPatternLength(5)
PrefixSpan...
>>> prefixSpan.findFrequentSequentialPatterns(df).sort("sequence").show(truncate=False)
+----------+----+
|sequence  |freq|
+----------+----+
|[[1]]     |3   |
|[[1], [3]]|2   |
|[[2]]     |3   |
|[[2, 1]]  |3   |
|[[3]]     |2   |
+----------+----+
...

Methods

`clear`(param)	Clears a param from the param map if it has been explicitly set.
`copy`([extra])	Creates a copy of this instance with the same uid and some extra params.
`explainParam`(param)	Explains a single param and returns its name, doc, and optional default value and user-supplied value in a string.
`explainParams`()	Returns the documentation of all params with their optionally default values and user-supplied values.
`extractParamMap`([extra])	Extracts the embedded default param values and user-supplied values, and then merges them with extra values from input into a flat param map, where the latter value is used if there exist conflicts, i.e., with ordering: default param values < user-supplied values < extra.
`findFrequentSequentialPatterns`(dataset)	Finds the complete set of frequent sequential patterns in the input sequences of itemsets.
`getMaxLocalProjDBSize`()	Gets the value of maxLocalProjDBSize or its default value.
`getMaxPatternLength`()	Gets the value of maxPatternLength or its default value.
`getMinSupport`()	Gets the value of minSupport or its default value.
`getOrDefault`(param)	Gets the value of a param in the user-supplied param map or its default value.
`getParam`(paramName)	Gets a param by its name.
`getSequenceCol`()	Gets the value of sequenceCol or its default value.
`hasDefault`(param)	Checks whether a param has a default value.
`hasParam`(paramName)	Tests whether this instance contains a param with a given (string) name.
`isDefined`(param)	Checks whether a param is explicitly set by user or has a default value.
`isSet`(param)	Checks whether a param is explicitly set by user.
`set`(param, value)	Sets a parameter in the embedded param map.
`setMaxLocalProjDBSize`(value)	Sets the value of `maxLocalProjDBSize`.
`setMaxPatternLength`(value)	Sets the value of `maxPatternLength`.
`setMinSupport`(value)	Sets the value of `minSupport`.
`setParams`(self, \*[, minSupport, …])	New in version 2.4.0.
`setSequenceCol`(value)	Sets the value of `sequenceCol`.

Attributes

`maxLocalProjDBSize`
`maxPatternLength`
`minSupport`
`params`	Returns all params ordered by name.
`sequenceCol`

Methods Documentation

clear(param)¶: Clears a param from the param map if it has been explicitly set.

copy(extra=None)¶

Creates a copy of this instance with the same uid and some extra params. This implementation first calls Params.copy and then make a copy of the companion Java pipeline component with extra params. So both the Python wrapper and the Java pipeline component get copied.

Parameters

extradict, optional: Extra parameters to copy to the new instance

Returns

JavaParams: Copy of this instance

explainParam(param)¶: Explains a single param and returns its name, doc, and optional default value and user-supplied value in a string.

explainParams()¶: Returns the documentation of all params with their optionally default values and user-supplied values.

extractParamMap(extra=None)¶

Extracts the embedded default param values and user-supplied values, and then merges them with extra values from input into a flat param map, where the latter value is used if there exist conflicts, i.e., with ordering: default param values < user-supplied values < extra.

Parameters

extradict, optional: extra param values

Returns

dict: merged param map

findFrequentSequentialPatterns(dataset)[source]¶

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

New in version 2.4.0.

Parameters

datasetpyspark.sql.DataFrame: A dataframe containing a sequence column which is ArrayType(ArrayType(T)) type, T is the item type for the input dataset.

Returns

pyspark.sql.DataFrame

A DataFrame that contains columns of sequence and corresponding frequency. The schema of it will be:

sequence: ArrayType(ArrayType(T)) (T is the item type)
freq: Long

getMaxLocalProjDBSize()[source]¶: Gets the value of maxLocalProjDBSize or its default value.

New in version 3.0.0.

getMaxPatternLength()[source]¶: Gets the value of maxPatternLength or its default value.

New in version 3.0.0.

getMinSupport()[source]¶: Gets the value of minSupport or its default value.

New in version 3.0.0.

getOrDefault(param)¶: Gets the value of a param in the user-supplied param map or its default value. Raises an error if neither is set.

getParam(paramName)¶: Gets a param by its name.

getSequenceCol()[source]¶: Gets the value of sequenceCol or its default value.

New in version 3.0.0.

hasDefault(param)¶: Checks whether a param has a default value.

hasParam(paramName)¶: Tests whether this instance contains a param with a given (string) name.

isDefined(param)¶: Checks whether a param is explicitly set by user or has a default value.

isSet(param)¶: Checks whether a param is explicitly set by user.

set(param, value)¶: Sets a parameter in the embedded param map.

setMaxLocalProjDBSize(value)[source]¶: Sets the value of maxLocalProjDBSize.

New in version 3.0.0.

setMaxPatternLength(value)[source]¶: Sets the value of maxPatternLength.

New in version 3.0.0.

setMinSupport(value)[source]¶: Sets the value of minSupport.

New in version 3.0.0.

setParams(self, \*, minSupport=0.1, maxPatternLength=10, maxLocalProjDBSize=32000000, sequenceCol="sequence")[source]¶: New in version 2.4.0.

setSequenceCol(value)[source]¶: Sets the value of sequenceCol.

New in version 3.0.0.

Attributes Documentation

maxLocalProjDBSize = Param(parent='undefined', name='maxLocalProjDBSize', doc='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. Must be > 0.')¶

maxPatternLength = Param(parent='undefined', name='maxPatternLength', doc='The maximal length of the sequential pattern. Must be > 0.')¶

minSupport = Param(parent='undefined', name='minSupport', doc='The minimal support level of the sequential pattern. Sequential pattern that appears more than (minSupport * size-of-the-dataset) times will be output. Must be >= 0.')¶

params¶: Returns all params ordered by name. The default implementation uses dir() to get all attributes of type Param.

sequenceCol = Param(parent='undefined', name='sequenceCol', doc='The name of the sequence column in dataset, rows with nulls in this column are ignored.')¶

FPGrowthModel ImageSchema