Population Standard Deviation : Math « Development Class « Java

1. Java
2. Development Class
3. Math

Population Standard Deviation

        
import java.util.Arrays;


/**
 * <p>Static methods for doing useful math</p><hr>
 *
 * @author  : $Author: brian $
 * @version : $Revision: 1.1 $
 *
 * <hr><p><font size="-1" color="#336699"><a href="http://www.mbari.org">
 * The Monterey Bay Aquarium Research Institute (MBARI)</a> provides this
 * documentation and code &quot;as is&quot;, with no warranty, express or
 * implied, of its quality or consistency. It is provided without support and
 * without obligation on the part of MBARI to assist in its use, correction,
 * modification, or enhancement. This information should not be published or
 * distributed to third parties without specific written permission from
 * MBARI.</font></p><br>
 *
 * <font size="-1" color="#336699">Copyright 2002 MBARI.<br>
 * MBARI Proprietary Information. All rights reserved.</font><br><hr><br>
 *
 */

public class Util{

    /**
     * Standard deviation is a statistical measure of spread or variability.The
     * standard deviation is the root mean square (RMS) deviation of the values
     * from their arithmetic mean.
     *
     * <b>populationStandardDeviation</b> normalizes values by N, where N is the sample size. This the
     * <i>Population Standard Deviation</i>
     * @param values
     * @return
     */
    public static strictfp double populationStandardDeviation(double[] values) {
        double mean = mean(values);
        double n = values.length;
        double dv = 0;
        for (double d : values) {
            double dm = d - mean;
            dv += dm * dm;
        }
        return Math.sqrt(dv / n);
    }


    /**
     * Calculate the mean of an array of values
     *
     * @param values The values to calculate
     * @return The mean of the values
     */
    public static strictfp double mean(double[] values) {
        return sum(values) / values.length;
    }
    /**
     * Sum up all the values in an array
     *
     * @param values an array of values
     * @return The sum of all values in the Array
     */
    public static strictfp double sum(double[] values) {
        if (values == null || values.length == 0) {
            throw new IllegalArgumentException("The data array either is null or does not contain any data.");
        }
        else {
            double sum = 0;
            for (int i = 0; i < values.length; i++) {
                sum += values[i];
            }
            return sum;
        }
    }
}

   
    
    
    
    
    
    
    
  

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