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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.ml.examples;

import org.apache.flink.ml.linalg.Vector;
import org.apache.flink.ml.linalg.Vectors;
import org.apache.flink.ml.linalg.typeinfo.VectorTypeInfo;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
import org.apache.flink.types.Row;
import org.apache.flink.util.CloseableIterator;

import java.util.Arrays;
import java.util.List;

import static org.apache.flink.ml.Functions.vectorToArray;
import static org.apache.flink.table.api.Expressions.$;

/** Simple program that converts a column of dense/sparse vectors into a column of double arrays. */
public class VectorToArrayExample {
    public static void main(String[] args) {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        StreamTableEnvironment tEnv = StreamTableEnvironment.create(env);

        // Generates input vector data.
        List vectors =
                Arrays.asList(
                        Vectors.dense(0.0, 0.0),
                        Vectors.sparse(2, new int[] {1}, new double[] {1.0}));
        Table inputTable =
                tEnv.fromDataStream(env.fromCollection(vectors, VectorTypeInfo.INSTANCE))
                        .as("vector");

        // Converts each vector to a double array.
        Table outputTable = inputTable.select($("vector"), vectorToArray($("vector")).as("array"));

        // Extracts and displays the results.
        for (CloseableIterator it = outputTable.execute().collect(); it.hasNext(); ) {
            Row row = it.next();
            Vector vector = row.getFieldAs("vector");
            Double[] doubleArray = row.getFieldAs("array");
            System.out.printf(
                    "Input vector: %s\tOutput double array: %s\n",
                    vector, Arrays.toString(doubleArray));
        }
    }
}