/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.math.stat.descriptive.moment; import java.io.Serializable; /** * Computes a statistic related to the Fourth Central Moment. Specifically, * what is computed is the sum of *
* (x_i - xbar) ^ 4,
** where the x_i are the * sample observations and xbar is the sample mean.
** The following recursive updating formula is used:
** Let
* new value = old value - 4 * (dev/n) * m3 + 6 * (dev/n)^2 * m2 +
* [n^2 - 3 * (n-1)] * dev^4 * (n-1) / n^3
* Returns Double.NaN
if no data values have been added and
* returns 0
if there is just one value in the data set.
* Note that this implementation is not synchronized. If
* multiple threads access an instance of this class concurrently, and at least
* one of the threads invokes the increment()
or
* clear()
method, it must be synchronized externally.
Neither source nor dest can be null.
* * @param source FourthMoment to copy * @param dest FourthMoment to copy to * @throws NullPointerException if either source or dest is null */ public static void copy(FourthMoment source, FourthMoment dest) { ThirdMoment.copy(source, dest); dest.m4 = source.m4; } }