Github user mengxr commented on a diff in the pull request: https://github.com/apache/spark/pull/11108#discussion_r56434127 --- Diff: examples/src/main/java/org/apache/spark/examples/mllib/JavaStratifiedSamplingExample.java --- @@ -0,0 +1,81 @@ +/* + * 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.examples.mllib; + +import org.apache.spark.SparkConf; +import org.apache.spark.api.java.JavaSparkContext; + +// $example on$ +import java.util.ArrayList; +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +import scala.Tuple2; + +import org.apache.spark.api.java.JavaPairRDD; +import org.apache.spark.api.java.function.VoidFunction; +// $example off$ + +public class JavaStratifiedSamplingExample { + public static void main(String[] args) { + + SparkConf conf = new SparkConf().setAppName("JavaStratifiedSamplingExample"); + JavaSparkContext jsc = new JavaSparkContext(conf); + + // $example on$ + List<Tuple2<Integer, Character>> list = new ArrayList<>(); + list.add(new Tuple2(1, 'a')); + list.add(new Tuple2(1, 'b')); + list.add(new Tuple2(2, 'c')); + list.add(new Tuple2(2, 'd')); + list.add(new Tuple2(2, 'e')); + list.add(new Tuple2(3, 'f')); + + // an RDD of any key value pairs JavaPairRDD<K, V> + JavaPairRDD<Integer, Character> data = jsc.parallelizePairs(list); + + // specify the exact fraction desired from each key Map<K, Object> + Map<Integer, Object> fractions = new HashMap<>(); + + fractions.put(1, 0.1); + fractions.put(2, 0.6); + fractions.put(3, 0.3); + + // Get an exact sample from each stratum + JavaPairRDD<Integer, Character> approxSample = + data.sampleByKey(false, fractions); // JavaPairRDD<K, V> + JavaPairRDD<Integer, Character> exactSample = + data.sampleByKeyExact(false, fractions); // JavaPairRDD<K, V> --- End diff -- remove comment
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