+++ /dev/null
-/*
- * Copyright (c) 2003-2005 The BISON Project
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * 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 Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- *
- */
-
-package peersim.util;
-
-/**
- * This class provides extended statistical informations about the inspected
- * distribution. In particular, it provides functions to compute the skewness
- * (the 3rd degree moment) and the kurtosis (4th degree moment).
- *
- * @author Gian Paolo Jesi
- */
-public class MomentStats extends IncrementalStats {
-
- private double cubicsum, quadsum; // incremental sums
-
- /** Calls {@link #reset} */
- public MomentStats() {
- reset();
- }
-
- public void reset() {
- super.reset();
- cubicsum = quadsum = 0.0;
- }
-
- public void add(double item, int k) {
- for(int i=0; i<k; ++i)
- {
- super.add(item,1);
- cubicsum += item * item * item;
- quadsum += item * cubicsum;
- }
- }
-
- /** Outputs on a single line the superclass statistics postfixed by the
- * current skewness and kurtosis.
- */
- public String toString() {
- return super.toString()+" "+getSkewness()+" "+getKurtosis();
- }
-
- /** Computes the skewness on the node values distribution and
- * returns the asymmetry coefficient. It gives an indication about the
- * distribution symmetry compared to the average.
- *
- *@return The skewness value as a double.
- */
- public double getSkewness() {
- int n = this.getN();
- double m3 = (((double)n) / (n-1)) * (cubicsum/n - Math.pow(getAverage(), 3) );
- return ( m3 / Math.pow(getStD(), 3 ) );
- }
-
- /** Computes the kurtosis on the node values distribution and
- * returns the flatness coefficient. It gives an indication about the
- * distribution sharpness or flatness.
- *
- * @return The kurtosis momentus value as a double.
- */
- public double getKurtosis(){
- int n = this.getN();
- double m4 = (((double)n) / (n-1)) * (quadsum/n - Math.pow(getAverage(), 4) );
- return ( m4 / Math.pow(getStD(), 4) )-3;
- }
-
-}
