Java List std stddev(List observations)

Description

Calculate sample deviation

License

Open Source License

Declaration

public static double stddev(List<Double> observations) 

Method Source Code

//package com.java2s;
/*//from   w ww  . j  ava 2  s  . co m
 * JGAAP -- a graphical program for stylometric authorship attribution
 * Copyright (C) 2009,2011 by Patrick Juola
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.List;

public class Main {
    /** Calculate sample deviation */
    public static double stddev(List<Double> observations) {

        // Catch single observation case
        if (observations.size() == 1) {
            return 0.0;
        }

        double mean = 0.0;

        // Calculate the mean of the observations
        for (Double d : observations) {
            mean += d;
        }
        mean = mean / observations.size();

        double stddev = 0.0;
        for (Double d : observations) {
            stddev += (d - mean) * (d - mean);
        }

        stddev = stddev / (observations.size() - 1); // Get the sample standard deviation
        return Math.sqrt(stddev);
    }
}

Related

1. standardDeviation(List values, double xbar)
2. standardDeviationDouble(List list, boolean populationStandardDeviation)
3. std(List iNumbers)
4. std(List vector, Double avg)
5. stdDev(List nums)
6. stDev(final List list)
7. stdev(List values)
8. stdInt(List elements)
9. varianceDouble(List list, boolean populationStandardDeviation)