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/*
* 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 com.google.common.collect.ImmutableMap;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaSparkContext;
// $example on$
import java.util.*;
import scala.Tuple2;
import org.apache.spark.api.java.JavaPairRDD;
// $example off$
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<Tuple2<Integer, Character>>(
Arrays.<Tuple2<Integer, Character>>asList(
new Tuple2(1, 'a'),
new Tuple2(1, 'b'),
new Tuple2(2, 'c'),
new Tuple2(2, 'd'),
new Tuple2(2, 'e'),
new Tuple2(3, 'f')
)
);
JavaPairRDD<Integer, Character> data = jsc.parallelizePairs(list);
// specify the exact fraction desired from each key Map<K, Object>
ImmutableMap<Integer, Object> fractions =
ImmutableMap.of(1, (Object)0.1, 2, (Object) 0.6, 3, (Object) 0.3);
// Get an approximate sample from each stratum
JavaPairRDD<Integer, Character> approxSample = data.sampleByKey(false, fractions);
// Get an exact sample from each stratum
JavaPairRDD<Integer, Character> exactSample = data.sampleByKeyExact(false, fractions);
// $example off$
System.out.println("approxSample size is " + approxSample.collect().size());
for (Tuple2<Integer, Character> t : approxSample.collect()) {
System.out.println(t._1() + " " + t._2());
}
System.out.println("exactSample size is " + exactSample.collect().size());
for (Tuple2<Integer, Character> t : exactSample.collect()) {
System.out.println(t._1() + " " + t._2());
}
jsc.stop();
}
}
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