statutils.java

Apache的common math数学软件包

/*
 * 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;

import org.apache.commons.math.stat.descriptive.UnivariateStatistic;
import org.apache.commons.math.stat.descriptive.moment.GeometricMean;
import org.apache.commons.math.stat.descriptive.moment.Mean;
import org.apache.commons.math.stat.descriptive.moment.Variance;
import org.apache.commons.math.stat.descriptive.rank.Max;
import org.apache.commons.math.stat.descriptive.rank.Min;
import org.apache.commons.math.stat.descriptive.rank.Percentile;
import org.apache.commons.math.stat.descriptive.summary.Product;
import org.apache.commons.math.stat.descriptive.summary.Sum;
import org.apache.commons.math.stat.descriptive.summary.SumOfLogs;
import org.apache.commons.math.stat.descriptive.summary.SumOfSquares;

/**
 * StatUtils provides static methods for computing statistics based on data
 * stored in double[] arrays. 
 * 
 * @version $Revision: 617953 $ $Date: 2008-02-02 22:54:00 -0700 (Sat, 02 Feb 2008) $
 */
public final class StatUtils {

    /** sum */
    private static UnivariateStatistic sum = new Sum();

    /** sumSq */
    private static UnivariateStatistic sumSq = new SumOfSquares();

    /** prod */
    private static UnivariateStatistic prod = new Product();

    /** sumLog */
    private static UnivariateStatistic sumLog = new SumOfLogs();

    /** min */
    private static UnivariateStatistic min = new Min();

    /** max */
    private static UnivariateStatistic max = new Max();

    /** mean */
    private static UnivariateStatistic mean = new Mean();

    /** variance */
    private static Variance variance = new Variance();

    /** percentile */
    private static Percentile percentile = new Percentile();
    
    /** geometric mean */
    private static GeometricMean geometricMean = new GeometricMean();

    /**
     * Private Constructor
     */
    private StatUtils() {
    }

    /**
     * Returns the sum of the values in the input array, or
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the input array
     * is null.</p>
     * 
     * @param values  array of values to sum
     * @return the sum of the values or <code>Double.NaN</code> if the array
     * is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double sum(final double[] values) {
        return sum.evaluate(values);
    }

    /**
     * Returns the sum of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the sum of the values or Double.NaN if length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     *  parameters are not valid
     */
    public static double sum(final double[] values, final int begin, 
            final int length) {
        return sum.evaluate(values, begin, length);
    }

    /**
     * Returns the sum of the squares of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values  input array
     * @return the sum of the squared values or <code>Double.NaN</code> if the
     * array is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double sumSq(final double[] values) {
        return sumSq.evaluate(values);
    }

    /**
     * Returns the sum of the squares of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the sum of the squares of the values or Double.NaN if length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     * parameters are not valid
     */
    public static double sumSq(final double[] values, final int begin,
            final int length) {
        return sumSq.evaluate(values, begin, length);
    }

    /**
     * Returns the product of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values the input array
     * @return the product of the values or Double.NaN if the array is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double product(final double[] values) {
        return prod.evaluate(values);
    }

    /**
     * Returns the product of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the product of the values or Double.NaN if length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     * parameters are not valid
     */
    public static double product(final double[] values, final int begin,
            final int length) {
        return prod.evaluate(values, begin, length);
    }

    /**
     * Returns the sum of the natural logs of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.summary.SumOfLogs}.
     * </p>
     * 
     * @param values the input array
     * @return the sum of the natural logs of the values or Double.NaN if 
     * the array is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double sumLog(final double[] values) {
        return sumLog.evaluate(values);
    }

    /**
     * Returns the sum of the natural logs of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.summary.SumOfLogs}.
     * </p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the sum of the natural logs of the values or Double.NaN if 
     * length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     * parameters are not valid
     */
    public static double sumLog(final double[] values, final int begin,
            final int length) {
        return sumLog.evaluate(values, begin, length);
    }

    /**
     * Returns the arithmetic mean of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.moment.Mean} for
     * details on the computing algorithm.</p>
     * 
     * @param values the input array
     * @return the mean of the values or Double.NaN if the array is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double mean(final double[] values) {
        return mean.evaluate(values);
    }

    /**
     * Returns the arithmetic mean of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.moment.Mean} for
     * details on the computing algorithm.</p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the mean of the values or Double.NaN if length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     * parameters are not valid
     */
    public static double mean(final double[] values, final int begin,
            final int length) {
        return mean.evaluate(values, begin, length);
    }
    
    /**
     * Returns the geometric mean of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.moment.GeometricMean}
     * for details on the computing algorithm.</p>
     * 
     * @param values the input array
     * @return the geometric mean of the values or Double.NaN if the array is empty
     * @throws IllegalArgumentException if the array is null
     */
    public static double geometricMean(final double[] values) {
        return geometricMean.evaluate(values);
    }

    /**
     * Returns the geometric mean of the entries in the specified portion of
     * the input array, or <code>Double.NaN</code> if the designated subarray
     * is empty.
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.moment.GeometricMean}
     * for details on the computing algorithm.</p>
     * 
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the geometric mean of the values or Double.NaN if length = 0
     * @throws IllegalArgumentException if the array is null or the array index
     * parameters are not valid
     */
    public static double geometricMean(final double[] values, final int begin,
            final int length) {
        return geometricMean.evaluate(values, begin, length);
    }
    

    /**
     * Returns the variance of the entries in the input array, or 
     * <code>Double.NaN</code> if the array is empty.
     * <p>
     * See {@link org.apache.commons.math.stat.descriptive.moment.Variance} for
     * details on the computing algorithm.</p>
     * <p>
     * Returns 0 for a single-value (i.e. length = 1) sample.</p>
     * <p>
     * Throws <code>IllegalArgumentException</code> if the array is null.</p>
     * 
     * @param values the input array
     * @return the variance of the values or Double.NaN if the array is empty
     * @throws IllegalArgumentException if the array is null
     */