Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/4504#discussion_r25232679
--- Diff: mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala
---
@@ -39,3 +39,66 @@ class Tokenizer extends UnaryTransformer[String,
Seq[String], Tokenizer] {
override protected def outputDataType: DataType = new
ArrayType(StringType, false)
}
+
+
+/**
+ * :: AlphaComponent ::
+ * A regex based tokenizer that extracts tokens using a regex.
+ * Optional additional parameters include enabling lowercase
stabdarization, a minimum character
+ * size for tokens as well as an array of stop words to remove from the
results.
+ */
+@AlphaComponent
+class RegexTokenizer extends UnaryTransformer[String, Seq[String],
RegexTokenizer] {
+
+ val lowerCase = new BooleanParam(this,
+ "lowerCase",
+ "enable case folding to lower case",
+ Some(true))
+ def setLowercase(value: Boolean) = set(lowerCase, value)
+ def getLowercase: Boolean = get(lowerCase)
+
+ val minLength = new IntParam(this,
--- End diff --
Add doc and update code style. What's the case when we match a token with
regex but its length is zero? Should we control it in the regex, e.g., `\d{5,}`?
Btw, it is not intuitive that the min value is excluded. Could we remove
"excluded" and set the default value to `1`? And it might be better to call it
`minTokenLength`, if we want to keep it.
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