Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/364#discussion_r11470221
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/evaluation/binary/BinaryClassificationMetrics.scala
---
@@ -0,0 +1,204 @@
+/*
+ * 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.mllib.evaluation.binary
+
+import org.apache.spark.rdd.{UnionRDD, RDD}
+import org.apache.spark.SparkContext._
+import org.apache.spark.mllib.evaluation.AreaUnderCurve
+import org.apache.spark.Logging
+
+/**
+ * Implementation of
[[org.apache.spark.mllib.evaluation.binary.BinaryConfusionMatrix]].
+ *
+ * @param count label counter for labels with scores greater than or equal
to the current score
+ * @param totalCount label counter for all labels
+ */
+private case class BinaryConfusionMatrixImpl(
+ count: LabelCounter,
+ totalCount: LabelCounter) extends BinaryConfusionMatrix with
Serializable {
+
+ /** number of true positives */
+ override def tp: Long = count.numPositives
+
+ /** number of false positives */
+ override def fp: Long = count.numNegatives
+
+ /** number of false negatives */
+ override def fn: Long = totalCount.numPositives - count.numPositives
+
+ /** number of true negatives */
+ override def tn: Long = totalCount.numNegatives - count.numNegatives
+
+ /** number of positives */
+ override def p: Long = totalCount.numPositives
+
+ /** number of negatives */
+ override def n: Long = totalCount.numNegatives
+}
+
+/**
+ * Evaluator for binary classification.
+ *
+ * @param scoreAndLabels an RDD of (score, label) pairs.
+ */
+class BinaryClassificationMetrics(scoreAndLabels: RDD[(Double, Double)])
+ extends Serializable with Logging {
+
+ private lazy val (
+ cumCounts: RDD[(Double, LabelCounter)],
+ confusions: RDD[(Double, BinaryConfusionMatrix)]) = {
+ // Create a bin for each distinct score value, count positives and
negatives within each bin,
+ // and then sort by score values in descending order.
+ val counts = scoreAndLabels.combineByKey(
+ createCombiner = (label: Double) => new LabelCounter(0L, 0L) +=
label,
+ mergeValue = (c: LabelCounter, label: Double) => c += label,
+ mergeCombiners = (c1: LabelCounter, c2: LabelCounter) => c1 += c2
+ ).sortByKey(ascending = false)
+ val agg = counts.values.mapPartitions({ iter =>
+ val agg = new LabelCounter()
+ iter.foreach(agg += _)
+ Iterator(agg)
+ }, preservesPartitioning = true).collect()
+ val partitionwiseCumCounts =
+ agg.scanLeft(new LabelCounter())((agg: LabelCounter, c:
LabelCounter) => agg.clone() += c)
--- End diff --
Actually there was one ... but scalastyle doesn't allow `def +(` because it
asks for a space after `+`.
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