[GitHub] [spark] huaxingao commented on a change in pull request #27527: [SPARK-30776][ML] Support FValueRegressionSelector for continuous features and continuous labels

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huaxingao commented on a change in pull request #27527: [SPARK-30776][ML] Support FValueRegressionSelector for continuous features and continuous labels
URL: https://github.com/apache/spark/pull/27527#discussion_r377241741
 
 

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 File path: mllib/src/main/scala/org/apache/spark/ml/feature/Selector.scala
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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 scala.collection.mutable.ArrayBuilder
+
+import org.apache.spark.annotation.Since
+import org.apache.spark.ml._
+import org.apache.spark.ml.attribute.{AttributeGroup, _}
+import org.apache.spark.ml.linalg._
+import org.apache.spark.ml.param._
+import org.apache.spark.ml.param.shared._
+import org.apache.spark.ml.stat.SelectionTestResult
+import org.apache.spark.ml.util._
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql._
+import org.apache.spark.sql.functions._
+import org.apache.spark.sql.types.{DoubleType, StructField, StructType}
+
+
+/**
+ * Params for [[Selector]] and [[SelectorModel]].
+ */
+private[feature] trait SelectorParams extends Params
+  with HasFeaturesCol with HasOutputCol with HasLabelCol {
+
+  /**
+   * Number of features that selector will select, ordered by ascending p-value. If the
+   * number of features is less than numTopFeatures, then this will select all features.
+   * Only applicable when selectorType = "numTopFeatures".
+   * The default value of numTopFeatures is 50.
+   *
+   * @group param
+   */
+  @Since("3.1.0")
+  final val numTopFeatures = new IntParam(this, "numTopFeatures",
+    "Number of features that selector will select, ordered by ascending p-value. If the" +
+      " number of features is < numTopFeatures, then this will select all features.",
+    ParamValidators.gtEq(1))
+  setDefault(numTopFeatures -> 50)
+
+  /** @group getParam */
+  @Since("3.1.0")
+  def getNumTopFeatures: Int = $(numTopFeatures)
+
+  /**
+   * Percentile of features that selector will select, ordered by ascending p-value.
+   * Only applicable when selectorType = "percentile".
+   * Default value is 0.1.
+   * @group param
+   */
 
 Review comment:
   In the original ChiSqSelector, the doc for percentile is this:
   ```
     /**
      * Percentile of features that selector will select, ordered by statistics value descending.
      * Only applicable when selectorType = "percentile".
      * Default value is 0.1.
      * @group param
      */
   ```
   I changed it to ```ordered by ascending p-value```because in the below definition 
   ```
     final val percentile = new DoubleParam(this, "percentile",
       "Percentile of features that selector will select, ordered by ascending p-value.",
   ```
   it has "ordered by ascending p-value". Also in the implementation of fit method, it uses pValue instead of statistics value.
   ```
         case "percentile" =>
           testResult
             .sortBy { case (res, _) => res.pValue }
             .take((testResult.length * getPercentile).toInt)
   ```
   

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