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 <a href=”https://doi.org/10.1109/ICDE.2001.914830”>here</a>). This class is not yet an Estimator/Transformer, use
findFrequentSequentialPatterns()
method to run the PrefixSpan algorithm.@see <a href=”https://en.wikipedia.org/wiki/Sequential_Pattern_Mining”>Sequential Pattern Mining (Wikipedia)</a>
>>> 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 | +----------+----+ ...
New in version 2.4.0.
Methods
Attributes
Methods Documentation
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clear
(param)¶ Clears a param from the param map if it has been explicitly set.
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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
extra – Extra parameters to copy to the new instance
- Returns
Copy of this instance
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explainParam
(param)¶ Explains a single param and returns its name, doc, and optional default value and user-supplied value in a string.
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explainParams
()¶ Returns the documentation of all params with their optionally default values and user-supplied values.
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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
extra – extra param values
- Returns
merged param map
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findFrequentSequentialPatterns
(dataset)[source]¶ Finds the complete set of frequent sequential patterns in the input sequences of itemsets.
- Parameters
dataset – A dataframe containing a sequence column which is ArrayType(ArrayType(T)) type, T is the item type for the input dataset.
- Returns
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
New in version 2.4.0.
New in version 2.4.0.
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getMaxLocalProjDBSize
()[source]¶ Gets the value of maxLocalProjDBSize or its default value.
New in version 3.0.0.
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getMaxPatternLength
()[source]¶ Gets the value of maxPatternLength or its default value.
New in version 3.0.0.
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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.
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getParam
(paramName)¶ Gets a param by its name.
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hasDefault
(param)¶ Checks whether a param has a default value.
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hasParam
(paramName)¶ Tests whether this instance contains a param with a given (string) name.
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isDefined
(param)¶ Checks whether a param is explicitly set by user or has a default value.
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isSet
(param)¶ Checks whether a param is explicitly set by user.
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set
(param, value)¶ Sets a parameter in the embedded param map.
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setMaxLocalProjDBSize
(value)[source]¶ Sets the value of
maxLocalProjDBSize
.New in version 3.0.0.
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setMaxPatternLength
(value)[source]¶ Sets the value of
maxPatternLength
.New in version 3.0.0.
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setMinSupport
(value)[source]¶ Sets the value of
minSupport
.New in version 3.0.0.
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setParams
(self, minSupport=0.1, maxPatternLength=10, maxLocalProjDBSize=32000000, sequenceCol='sequence')[source]¶ New in version 2.4.0.
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setSequenceCol
(value)[source]¶ Sets the value of
sequenceCol
.New in version 3.0.0.
Attributes Documentation
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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.')¶
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maxPatternLength
= Param(parent='undefined', name='maxPatternLength', doc='The maximal length of the sequential pattern. Must be > 0.')¶
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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.')¶
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params
¶ Returns all params ordered by name. The default implementation uses
dir()
to get all attributes of typeParam
.
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sequenceCol
= Param(parent='undefined', name='sequenceCol', doc='The name of the sequence column in dataset, rows with nulls in this column are ignored.')¶
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