Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/11108#discussion_r56435169
--- Diff:
examples/src/main/scala/org/apache/spark/examples/mllib/StratifiedSamplingExample.scala
---
@@ -0,0 +1,50 @@
+/*
+ * 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.
+ */
+
+// scalastyle:off println
+package org.apache.spark.examples.mllib
+
+import org.apache.spark.{SparkConf, SparkContext}
+
+object StratifiedSamplingExample {
+
+ def main(args: Array[String]): Unit = {
+
+ val conf = new SparkConf().setAppName("StratifiedSamplingExample")
+ val sc = new SparkContext(conf)
+
+ // $example on$
+ // an RDD[(K, V)] of any key value pairs
+ val data = sc.parallelize(
+ Seq((1, 'a'), (1, 'b'), (2, 'c'), (2, 'd'), (2, 'e'), (3, 'f')))
+
+ // specify the exact fraction desired from each key
+ val fractions = Map(1 -> 0.1, 2 -> 0.6, 3 -> 0.3)
+
+ // Get an exact sample from each stratum
+ val approxSample = data.sampleByKey(withReplacement = false, fractions)
+ val exactSample = data.sampleByKeyExact(withReplacement = false,
fractions)
+ // $example off$
+
+ approxSample.foreach(println)
--- End diff --
It would be useful to print a header to say which one is approx and which
is exact.
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