1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
|
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.ml.feature
import org.apache.spark.annotation.{Experimental, Since}
import org.apache.spark.ml.Transformer
import org.apache.spark.ml.param.{BooleanParam, ParamMap, StringArrayParam}
import org.apache.spark.ml.param.shared.{HasInputCol, HasOutputCol}
import org.apache.spark.ml.util._
import org.apache.spark.sql.{DataFrame, Dataset}
import org.apache.spark.sql.functions.{col, udf}
import org.apache.spark.sql.types.{ArrayType, StringType, StructType}
/**
* :: Experimental ::
* A feature transformer that filters out stop words from input.
* Note: null values from input array are preserved unless adding null to stopWords explicitly.
* @see [[http://en.wikipedia.org/wiki/Stop_words]]
*/
@Experimental
@Since("1.5.0")
class StopWordsRemover @Since("1.5.0") (@Since("1.5.0") override val uid: String)
extends Transformer with HasInputCol with HasOutputCol with DefaultParamsWritable {
@Since("1.5.0")
def this() = this(Identifiable.randomUID("stopWords"))
/** @group setParam */
@Since("1.5.0")
def setInputCol(value: String): this.type = set(inputCol, value)
/** @group setParam */
@Since("1.5.0")
def setOutputCol(value: String): this.type = set(outputCol, value)
/**
* The words to be filtered out.
* Default: English stop words
* @see [[StopWordsRemover.loadDefaultStopWords()]]
* @group param
*/
@Since("1.5.0")
val stopWords: StringArrayParam =
new StringArrayParam(this, "stopWords", "the words to be filtered out")
/** @group setParam */
@Since("1.5.0")
def setStopWords(value: Array[String]): this.type = set(stopWords, value)
/** @group getParam */
@Since("1.5.0")
def getStopWords: Array[String] = $(stopWords)
/**
* Whether to do a case sensitive comparison over the stop words.
* Default: false
* @group param
*/
@Since("1.5.0")
val caseSensitive: BooleanParam = new BooleanParam(this, "caseSensitive",
"whether to do a case-sensitive comparison over the stop words")
/** @group setParam */
@Since("1.5.0")
def setCaseSensitive(value: Boolean): this.type = set(caseSensitive, value)
/** @group getParam */
@Since("1.5.0")
def getCaseSensitive: Boolean = $(caseSensitive)
setDefault(stopWords -> StopWordsRemover.loadDefaultStopWords("english"), caseSensitive -> false)
@Since("2.0.0")
override def transform(dataset: Dataset[_]): DataFrame = {
val outputSchema = transformSchema(dataset.schema)
val t = if ($(caseSensitive)) {
val stopWordsSet = $(stopWords).toSet
udf { terms: Seq[String] =>
terms.filter(s => !stopWordsSet.contains(s))
}
} else {
// TODO: support user locale (SPARK-15064)
val toLower = (s: String) => if (s != null) s.toLowerCase else s
val lowerStopWords = $(stopWords).map(toLower(_)).toSet
udf { terms: Seq[String] =>
terms.filter(s => !lowerStopWords.contains(toLower(s)))
}
}
val metadata = outputSchema($(outputCol)).metadata
dataset.select(col("*"), t(col($(inputCol))).as($(outputCol), metadata))
}
@Since("1.5.0")
override def transformSchema(schema: StructType): StructType = {
val inputType = schema($(inputCol)).dataType
require(inputType.sameType(ArrayType(StringType)),
s"Input type must be ArrayType(StringType) but got $inputType.")
SchemaUtils.appendColumn(schema, $(outputCol), inputType, schema($(inputCol)).nullable)
}
@Since("1.5.0")
override def copy(extra: ParamMap): StopWordsRemover = defaultCopy(extra)
}
@Since("1.6.0")
object StopWordsRemover extends DefaultParamsReadable[StopWordsRemover] {
private[feature]
val supportedLanguages = Set("danish", "dutch", "english", "finnish", "french", "german",
"hungarian", "italian", "norwegian", "portuguese", "russian", "spanish", "swedish", "turkish")
@Since("1.6.0")
override def load(path: String): StopWordsRemover = super.load(path)
/**
* Loads the default stop words for the given language.
* Supported languages: danish, dutch, english, finnish, french, german, hungarian,
* italian, norwegian, portuguese, russian, spanish, swedish, turkish
* @see [[http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/snowball/stopwords/]]
*/
@Since("2.0.0")
def loadDefaultStopWords(language: String): Array[String] = {
require(supportedLanguages.contains(language),
s"$language is not in the supported language list: ${supportedLanguages.mkString(", ")}.")
val is = getClass.getResourceAsStream(s"/org/apache/spark/ml/feature/stopwords/$language.txt")
scala.io.Source.fromInputStream(is)(scala.io.Codec.UTF8).getLines().toArray
}
}
|
