add PredictionAndResponse

mllib/src/main/scala/org/apache/spark/mllib/evaluation/PredictionAndResponse.scala

@@ -0,0 +1,34 @@
+/*
+ * 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
+
+/**
+ * Wrapper for (prediction/score, response/label) pairs.
+ *
+ * @param prediction prediction
+ * @param response true response
+ * @tparam P prediction type
+ * @tparam R response/label type
+ */
+case class PredictionAndResponse[@specialized(Double) P, @specialized(Double) R](prediction: P, response: R) {
+  /** Alias for prediction. */
+  def score: P = prediction
+
+  /** Alias for response. */
+  def label: R = response
+}