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/*
* 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.UnaryTransformer
import org.apache.spark.ml.param._
import org.apache.spark.ml.util._
import org.apache.spark.sql.types.{ArrayType, DataType, StringType}
/**
* :: Experimental ::
* A tokenizer that converts the input string to lowercase and then splits it by white spaces.
*
* @see [[RegexTokenizer]]
*/
@Experimental
class Tokenizer(override val uid: String)
extends UnaryTransformer[String, Seq[String], Tokenizer] with DefaultParamsWritable {
def this() = this(Identifiable.randomUID("tok"))
override protected def createTransformFunc: String => Seq[String] = {
_.toLowerCase.split("\\s")
}
override protected def validateInputType(inputType: DataType): Unit = {
require(inputType == StringType, s"Input type must be string type but got $inputType.")
}
override protected def outputDataType: DataType = new ArrayType(StringType, true)
override def copy(extra: ParamMap): Tokenizer = defaultCopy(extra)
}
@Since("1.6.0")
object Tokenizer extends DefaultParamsReadable[Tokenizer] {
@Since("1.6.0")
override def load(path: String): Tokenizer = super.load(path)
}
/**
* :: Experimental ::
* A regex based tokenizer that extracts tokens either by using the provided regex pattern to split
* the text (default) or repeatedly matching the regex (if `gaps` is false).
* Optional parameters also allow filtering tokens using a minimal length.
* It returns an array of strings that can be empty.
*/
@Experimental
class RegexTokenizer(override val uid: String)
extends UnaryTransformer[String, Seq[String], RegexTokenizer] with DefaultParamsWritable {
def this() = this(Identifiable.randomUID("regexTok"))
/**
* Minimum token length, >= 0.
* Default: 1, to avoid returning empty strings
* @group param
*/
val minTokenLength: IntParam = new IntParam(this, "minTokenLength", "minimum token length (>= 0)",
ParamValidators.gtEq(0))
/** @group setParam */
def setMinTokenLength(value: Int): this.type = set(minTokenLength, value)
/** @group getParam */
def getMinTokenLength: Int = $(minTokenLength)
/**
* Indicates whether regex splits on gaps (true) or matches tokens (false).
* Default: true
* @group param
*/
val gaps: BooleanParam = new BooleanParam(this, "gaps", "Set regex to match gaps or tokens")
/** @group setParam */
def setGaps(value: Boolean): this.type = set(gaps, value)
/** @group getParam */
def getGaps: Boolean = $(gaps)
/**
* Regex pattern used to match delimiters if [[gaps]] is true or tokens if [[gaps]] is false.
* Default: `"\\s+"`
* @group param
*/
val pattern: Param[String] = new Param(this, "pattern", "regex pattern used for tokenizing")
/** @group setParam */
def setPattern(value: String): this.type = set(pattern, value)
/** @group getParam */
def getPattern: String = $(pattern)
/**
* Indicates whether to convert all characters to lowercase before tokenizing.
* Default: true
* @group param
*/
final val toLowercase: BooleanParam = new BooleanParam(this, "toLowercase",
"whether to convert all characters to lowercase before tokenizing.")
/** @group setParam */
def setToLowercase(value: Boolean): this.type = set(toLowercase, value)
/** @group getParam */
def getToLowercase: Boolean = $(toLowercase)
setDefault(minTokenLength -> 1, gaps -> true, pattern -> "\\s+", toLowercase -> true)
override protected def createTransformFunc: String => Seq[String] = { originStr =>
val re = $(pattern).r
val str = if ($(toLowercase)) originStr.toLowerCase() else originStr
val tokens = if ($(gaps)) re.split(str).toSeq else re.findAllIn(str).toSeq
val minLength = $(minTokenLength)
tokens.filter(_.length >= minLength)
}
override protected def validateInputType(inputType: DataType): Unit = {
require(inputType == StringType, s"Input type must be string type but got $inputType.")
}
override protected def outputDataType: DataType = new ArrayType(StringType, true)
override def copy(extra: ParamMap): RegexTokenizer = defaultCopy(extra)
}
@Since("1.6.0")
object RegexTokenizer extends DefaultParamsReadable[RegexTokenizer] {
@Since("1.6.0")
override def load(path: String): RegexTokenizer = super.load(path)
}
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