An application I'm writing has a need to calculate RMS values for series of numbers. I can achieve this via `SummaryStatistics.getQuadraticMean`, but I'm left wondering why there isn't a corresponding `UnivariateStatistic` subclass? It seems to me that a QuadraticMean class within the org.apache.commons.math3.stat.descriptive.moment package <http://commons.apache.org/proper/commons-math/apidocs/org/apache/commons/math3/stat/descriptive/moment/package-summary.html> would be a reasonable addition to commons-math3.
Would be willing to implement one if there's agreement that it's worth introducing. -- Evan Meagher
