Github user yinxusen commented on a diff in the pull request: https://github.com/apache/spark/pull/11132#discussion_r53390121 --- Diff: examples/src/main/java/org/apache/spark/examples/mllib/JavaPCAExample.java --- @@ -0,0 +1,65 @@ +/* + * 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; + +// $example on$ +import java.util.LinkedList; +// $example off$ + +import org.apache.spark.SparkConf; +import org.apache.spark.SparkContext; +// $example on$ +import org.apache.spark.api.java.JavaRDD; +import org.apache.spark.api.java.JavaSparkContext; +import org.apache.spark.mllib.linalg.Matrix; +import org.apache.spark.mllib.linalg.Vector; +import org.apache.spark.mllib.linalg.Vectors; +import org.apache.spark.mllib.linalg.distributed.RowMatrix; +// $example off$ + +/** + * Example for compute principal components on a 'RowMatrix'. + */ +public class JavaPCAExample { + public static void main(String[] args) { + SparkConf conf = new SparkConf().setAppName("PCA Example"); + SparkContext sc = new SparkContext(conf); + + // $example on$ + double[][] array = {{1.12, 2.05, 3.12}, {5.56, 6.28, 8.94}, {10.2, 8.0, 20.5}}; + LinkedList<Vector> rowsList = new LinkedList<Vector>(); + for (int i = 0; i < array.length; i++) { + Vector currentRow = Vectors.dense(array[i]); + rowsList.add(currentRow); + } + JavaRDD<Vector> rows = JavaSparkContext.fromSparkContext(sc).parallelize(rowsList); + + // Create a RowMatrix from JavaRDD<Vector>. + RowMatrix mat = new RowMatrix(rows.rdd()); + + // Compute the top 3 principal components. + Matrix pc = mat.computePrincipalComponents(3); + RowMatrix projected = mat.multiply(pc); --- End diff -- Move the // $example off$ here
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