Computes the (bias-corrected sample) variance. - Java Collection Framework

Java examples for Collection Framework:Array Algorithm

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Description

Computes the (bias-corrected sample) variance.

Demo Code


//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        double[] v = new double[] { 34.45, 35.45, 36.67, 37.78, 37.0000,
                37.1234, 67.2344, 68.34534, 69.87700 };
        System.out.println(variance(v));
    }/*from  w w  w .jav a  2 s. c  om*/

    /**
     * Computes the (bias-corrected sample) variance.
     */
    public static double variance(double[] v) {
        if (v.length > 1) {
            final double m = mean(v);
            double ans = 0.0;
            for (int i = 0; i < v.length; i++)
                ans += (v[i] - m) * (v[i] - m);
            return ans / (v.length - 1);
        } else
            throw new IllegalArgumentException(
                    "Array length must be of 2 or greater.");
    }

    /**
     * Computes the (bias-corrected sample) variance.
     */
    public static double variance(int[] v) {
        if (v.length > 1) {
            final double m = mean(v);
            double ans = 0.0;
            for (int i = 0; i < v.length; i++)
                ans += (v[i] - m) * (v[i] - m);
            return ans / (v.length - 1);
        } else
            throw new IllegalArgumentException(
                    "Array length must be of 2 or greater.");
    }

    /**
     * Computes the mean.
     */
    public static double mean(double[] v) {
        if (v.length == 0)
            throw new IllegalArgumentException(
                    "Nothing to compute! The array must have at least one element.");
        return (mass(v) / (double) v.length);
    }

    /**
     * Computes the mean.
     */
    public static double mean(int[] v) {
        if (v.length == 0)
            throw new IllegalArgumentException(
                    "Nothing to compute! The array must have at least one element.");
        return (mass(v) / (double) v.length);
    }

    /**
     * Returns the sum of the elements of the array.
     */
    public static double mass(double[] v) {
        double somme = 0.0;
        for (int k = 0; k < v.length; k++) {
            somme += v[k];
        }
        return (somme);
    }

    /**
     * Returns the sum of the elements of the array.
     */
    public static int mass(int[] v) {
        int somme = 0;
        for (int k = 0; k < v.length; k++) {
            somme += v[k];
        }
        return (somme);
    }
}

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