[GitHub] [spark] huaxingao commented on a change in pull request #28710: [SPARK-31893][ML] Add a generic ClassificationSummary trait

[GitBox <gi...@apache.org>]

huaxingao commented on a change in pull request #28710:
URL: https://github.com/apache/spark/pull/28710#discussion_r434212285



##########
File path: mllib/src/main/scala/org/apache/spark/ml/classification/ClassificationSummary.scala
##########
@@ -0,0 +1,271 @@
+/*
+ * 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.classification
+
+import org.apache.spark.annotation.Since
+import org.apache.spark.ml.functions.checkNonNegativeWeight
+import org.apache.spark.ml.linalg.Vector
+import org.apache.spark.mllib.evaluation.{BinaryClassificationMetrics, MulticlassMetrics}
+import org.apache.spark.sql.{DataFrame, Row}
+import org.apache.spark.sql.functions.{col, lit}
+import org.apache.spark.sql.types.DoubleType
+
+
+/**
+ * Abstraction for multiclass classification results for a given model.
+ */
+private[classification] trait ClassificationSummary extends Serializable {
+
+  /**
+   * Dataframe output by the model's `transform` method.
+   */
+  @Since("3.1.0")
+  def predictions: DataFrame
+
+  /** Field in "predictions" which gives the prediction of each class. */
+  @Since("3.1.0")
+  def predictionCol: String
+
+  /** Field in "predictions" which gives the true label of each instance (if available). */
+  @Since("3.1.0")
+  def labelCol: String
+
+  /** Field in "predictions" which gives the features of each instance as a vector. */
+  @Since("3.1.0")
+  def featuresCol: String
+
+  /** Field in "predictions" which gives the weight of each instance as a vector. */
+  @Since("3.1.0")
+  def weightCol: String
+
+  @transient private val multiclassMetrics = {
+    if (predictions.schema.fieldNames.contains(weightCol)) {
+      new MulticlassMetrics(
+        predictions.select(
+          col(predictionCol),
+          col(labelCol).cast(DoubleType),
+          checkNonNegativeWeight(col(weightCol).cast(DoubleType))).rdd.map {
+          case Row(prediction: Double, label: Double, weight: Double) => (prediction, label, weight)
+        })
+    } else {
+      new MulticlassMetrics(
+        predictions.select(
+          col(predictionCol),
+          col(labelCol).cast(DoubleType),
+          lit(1.0)).rdd.map {
+          case Row(prediction: Double, label: Double, weight: Double) => (prediction, label, weight)
+        })
+    }
+  }
+
+  /**
+   * Returns the sequence of labels in ascending order. This order matches the order used
+   * in metrics which are specified as arrays over labels, e.g., truePositiveRateByLabel.
+   *
+   * Note: In most cases, it will be values {0.0, 1.0, ..., numClasses-1}, However, if the
+   * training set is missing a label, then all of the arrays over labels
+   * (e.g., from truePositiveRateByLabel) will be of length numClasses-1 instead of the
+   * expected numClasses.
+   */
+  @Since("3.1.0")
+  def labels: Array[Double] = multiclassMetrics.labels
+
+  /** Returns true positive rate for each label (category). */
+  @Since("3.1.0")
+  def truePositiveRateByLabel: Array[Double] = recallByLabel
+
+  /** Returns false positive rate for each label (category). */
+  @Since("3.1.0")
+  def falsePositiveRateByLabel: Array[Double] = {
+    multiclassMetrics.labels.map(label => multiclassMetrics.falsePositiveRate(label))
+  }
+
+  /** Returns precision for each label (category). */
+  @Since("3.1.0")
+  def precisionByLabel: Array[Double] = {
+    multiclassMetrics.labels.map(label => multiclassMetrics.precision(label))
+  }
+
+  /** Returns recall for each label (category). */
+  @Since("3.1.0")
+  def recallByLabel: Array[Double] = {
+    multiclassMetrics.labels.map(label => multiclassMetrics.recall(label))
+  }
+
+  /** Returns f-measure for each label (category). */
+  @Since("3.1.0")
+  def fMeasureByLabel(beta: Double): Array[Double] = {
+    multiclassMetrics.labels.map(label => multiclassMetrics.fMeasure(label, beta))
+  }
+
+  /** Returns f1-measure for each label (category). */
+  @Since("3.1.0")
+  def fMeasureByLabel: Array[Double] = fMeasureByLabel(1.0)
+
+  /**
+   * Returns accuracy.
+   * (equals to the total number of correctly classified instances
+   * out of the total number of instances.)
+   */
+  @Since("3.1.0")
+  def accuracy: Double = multiclassMetrics.accuracy
+
+  /**
+   * Returns weighted true positive rate.
+   * (equals to precision, recall and f-measure)
+   */
+  @Since("3.1.0")
+  def weightedTruePositiveRate: Double = weightedRecall
+
+  /** Returns weighted false positive rate. */
+  @Since("3.1.0")
+  def weightedFalsePositiveRate: Double = multiclassMetrics.weightedFalsePositiveRate
+
+  /**
+   * Returns weighted averaged recall.
+   * (equals to precision, recall and f-measure)
+   */
+  @Since("3.1.0")
+  def weightedRecall: Double = multiclassMetrics.weightedRecall
+
+  /** Returns weighted averaged precision. */
+  @Since("3.1.0")
+  def weightedPrecision: Double = multiclassMetrics.weightedPrecision
+
+  /** Returns weighted averaged f-measure. */
+  @Since("3.1.0")
+  def weightedFMeasure(beta: Double): Double = multiclassMetrics.weightedFMeasure(beta)
+
+  /** Returns weighted averaged f1-measure. */
+  @Since("3.1.0")
+  def weightedFMeasure: Double = multiclassMetrics.weightedFMeasure(1.0)
+
+  /**
+   * Convenient method for casting to binary classification summary.
+   * This method will throw an Exception if the summary is not a binary summary.
+   */
+  @Since("3.1.0")
+  def asBinary: BinaryClassificationSummary = this match {
+    case b: BinaryClassificationSummary => b
+    case _ =>
+      throw new RuntimeException("Cannot cast to a binary summary.")
+  }
+}
+
+/**
+ * Abstraction for multiclass classification training results.
+ */
+private[classification] trait ClassificationTrainingSummary extends ClassificationSummary {
+
+  /** objective function (scaled loss + regularization) at each iteration. */
+  @Since("3.1.0")
+  def objectiveHistory: Array[Double]
+
+  /** Number of training iterations. */
+  @Since("3.1.0")
+  def totalIterations: Int = objectiveHistory.length
+}
+
+/**
+ * Abstraction for binary classification results for a given model.
+ */
+trait BinaryClassificationSummary extends ClassificationSummary {
+
+  private val sparkSession = predictions.sparkSession
+  import sparkSession.implicits._
+
+  /**
+   * Field in "predictions" which gives the probability or rawPrediction of each class as a vector.
+   */
+  @Since("3.1.0")
+  def scoreCol: String

Review comment:
       Can't name it to ```probabilityCol``` because not all the classifiers have ```probabilityCol```. If no  ```probability```, will use ```rawPrediction``` instead  to calculate the binary classification metrics. 




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