Mega Code Archive
Standard deviation is a statistical measure of spread or variability
<![CDATA[
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 "as is", 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 This information should not be published or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>standardDeviation</b> normalizes values by (N-1), where N is the sample size. This is the
* sqrt of an unbiased estimator of the variance of the population from
* which X is drawn, as long as X consists of independent, identically
* distributed samples.
*
* @param values
* @return
*/
public static strictfp double standardDeviation(double[] values) {
double mean = mean(values);
double dv = 0D;
for (double d : values) {
double dm = d - mean;
dv += dm * dm;
}
return Math.sqrt(dv / (values.length - 1));
// double[] deviation = deviationFromMean(values);
// double s = 0D;
// for (double d : deviation) {
// s += (d * d);
// }
// return Math.sqrt(s / values.length - 1);
}
/**
* 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;
}
}
}
]]>