[GitHub] [spark] huaxingao commented on a change in pull request #27679: [SPARK-30776][ML] Support FValueSelector for continuous features and continuous labels

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huaxingao commented on a change in pull request #27679: [SPARK-30776][ML] Support FValueSelector for continuous features and continuous labels
URL: https://github.com/apache/spark/pull/27679#discussion_r387218344
 
 

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 File path: mllib/src/main/scala/org/apache/spark/ml/stat/SelectionTestResult.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.stat
+
+import org.apache.spark.annotation.Since
+
+/**
+ * Trait for selection test results.
+ */
+@Since("3.1.0")
+trait SelectionTestResult {
+
+  /**
+   * The probability of obtaining a test statistic result at least as extreme as the one that was
+   * actually observed, assuming that the null hypothesis is true.
+   */
+  @Since("3.1.0")
+  def pValue: Double
+
+  /**
+   * Test statistic.
+   * In ChiSqSelector, this is chi square statistic
+   * In ANOVASelector and FValueSelector, this is F Value
+   */
+  @Since("3.1.0")
+  def statistic: Double
+
+  /**
+   * Returns the degrees of freedom of the hypothesis test.
+   */
+  @Since("3.1.0")
+  def degreesOfFreedom: Long
+
+  /**
+   * String explaining the hypothesis test result.
+   * Specific classes implementing this trait should override this method to output test-specific
+   * information.
+   */
+  override def toString: String = {
+
+    // String explaining what the p-value indicates.
+    val pValueExplain = if (pValue <= 0.01) {
+      s"Very strong presumption against null hypothesis."
+    } else if (0.01 < pValue && pValue <= 0.05) {
+      s"Strong presumption against null hypothesis."
+    } else if (0.05 < pValue && pValue <= 0.1) {
+      s"Low presumption against null hypothesis."
+    } else {
+      s"No presumption against null hypothesis."
+    }
+
+    s"degrees of freedom = ${degreesOfFreedom.toString} \n" + s"pValue = $pValue \n" + pValueExplain
+  }
+}
+
+/**
+ * Object containing the test results for the chi-squared hypothesis test.
+ */
+@Since("3.1.0")
+class ChiSqTestResult private[stat] (
+    override val pValue: Double,
+    override val degreesOfFreedom: Long,
+    override val statistic: Double) extends SelectionTestResult {
+
+  override def toString: String = {
+    "Chi square test summary:\n" +
+      super.toString +
+      s"Chi square statistic = $statistic \n"
+  }
+}
+
+/**
+ * Object containing the test results for the FValue regression test.
+ */
+@Since("3.1.0")
+class FValueRegressionTestResult private[stat] (
 
 Review comment:
   Updated.

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