Java List Variance variance(ArrayList doubleArrayList)

Description

variance

License

Open Source License

Declaration

public static double variance(ArrayList<Double> doubleArrayList) 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * The MIT License (MIT)/*  w  w  w  .j  a v a 2  s. co  m*/
 *
 * Copyright (c) Zhiya Zuo 2016
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *******************************************************************************/

import java.util.Arrays;
import java.util.ArrayList;

public class Main {
    public static double variance(ArrayList<Double> doubleArrayList) {
        // mean of a double array
        return variance(doubleArrayList.stream().mapToDouble(Double::doubleValue).toArray());
    }

    public static double variance(double[] doubleArray) {
        //{{{ sample variance of a double array
        double sumSquare = 0;
        double avg = mean(doubleArray);
        for (int i = 0; i < doubleArray.length; i++) {
            sumSquare += (doubleArray[i] - avg) * (doubleArray[i] - avg);
        }
        //}}}
        return sumSquare / (doubleArray.length - 1);
    }

    public static double mean(double[] doubleArray) {
        // mean of a double array
        return _sum(doubleArray) / doubleArray.length;
    }

    public static double mean(ArrayList<Double> doubleArrayList) {
        // mean of a double array
        return mean(doubleArrayList.stream().mapToDouble(Double::doubleValue).toArray());
    }

    private static double _sum(int[] intArray) {
        double[] doubleArray = Arrays.stream(intArray).asDoubleStream().toArray();
        return _sum(doubleArray);
    }

    private static double _sum(double[] doubleArray) {
        // Sum the elements in a doubel array
        double arraySum = 0;
        for (int i = 0; i < doubleArray.length; i++) {
            arraySum += doubleArray[i];
        }
        return arraySum;
    }
}

Related

1. variance(final List list)
2. variance(List data)
3. variance(List observations)
4. variance(List values)