/*
 * 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}
// $example on$
import org.apache.spark.mllib.linalg._
import org.apache.spark.mllib.stat.Statistics
import org.apache.spark.rdd.RDD
// $example off$

object CorrelationsExample {

  def main(args: Array[String]): Unit = {

    val conf = new SparkConf().setAppName("CorrelationsExample")
    val sc = new SparkContext(conf)

    // $example on$
    val seriesX: RDD[Double] = sc.parallelize(Array(1, 2, 3, 3, 5))  // a series
    // must have the same number of partitions and cardinality as seriesX
    val seriesY: RDD[Double] = sc.parallelize(Array(11, 22, 33, 33, 555))

    // compute the correlation using Pearson's method. Enter "spearman" for Spearman's method. If a
    // method is not specified, Pearson's method will be used by default.
    val correlation: Double = Statistics.corr(seriesX, seriesY, "pearson")
    println(s"Correlation is: $correlation")

    val data: RDD[Vector] = sc.parallelize(
      Seq(
        Vectors.dense(1.0, 10.0, 100.0),
        Vectors.dense(2.0, 20.0, 200.0),
        Vectors.dense(5.0, 33.0, 366.0))
    )  // note that each Vector is a row and not a column

    // calculate the correlation matrix using Pearson's method. Use "spearman" for Spearman's method
    // If a method is not specified, Pearson's method will be used by default.
    val correlMatrix: Matrix = Statistics.corr(data, "pearson")
    println(correlMatrix.toString)
    // $example off$

    sc.stop()
  }
}
// scalastyle:on println

