/* * 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; import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic; /** * Computes the first moment (arithmetic mean). Uses the definitional formula: *
* mean = sum(x_i) / n
*
* where n
is the number of observations.
* To limit numeric errors, the value of the statistic is computed using the * following recursive updating algorithm:
**
m =
the first valuem = m + (new value - m) / (number of observations)
* Returns Double.NaN
if the dataset is empty.
* 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 FirstMoment to copy * @param dest FirstMoment to copy to * @throws NullPointerException if either source or dest is null */ public static void copy(FirstMoment source, FirstMoment dest) { dest.setData(source.getDataRef()); dest.n = source.n; dest.m1 = source.m1; dest.dev = source.dev; dest.nDev = source.nDev; } }