-Mark
Index: StatUtils.java =================================================================== RCS file: StatUtils.java diff -N StatUtils.java --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ StatUtils.java 17 Jun 2003 19:17:26 -0000 @@ -0,0 +1,135 @@ +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2003 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, if + * any, must include the following acknowlegement: + * "This product includes software developed by the + * Apache Software Foundation (http://www.apache.org/)." + * Alternately, this acknowlegement may appear in the software itself, + * if and wherever such third-party acknowlegements normally appear. + * + * 4. The names "The Jakarta Project", "Commons", and "Apache Software + * Foundation" must not be used to endorse or promote products derived + * from this software without prior written permission. For written + * permission, please contact [EMAIL PROTECTED] + * + * 5. Products derived from this software may not be called "Apache" + * nor may "Apache" appear in their names without prior written + * permission of the Apache Software Foundation. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * <http://www.apache.org/>. + */ +package org.apache.commons.math.stat; + +/** + * StatUtils provides fast static implementation of common double[] based + * statistical methods + * + * @author <a href="mailto:[EMAIL PROTECTED]">Mark Diggory</a> + */ +public class StatUtils { + + public static int getN(double[] values) { + return values.length; + } + + public static double getSum(double[] values) { + double accum = 0.0; + for (int i = 0; i < getN(values); i++) { + accum += values[i]; + } + return accum; + } + + public static double getSumSq(double[] values) { + double accum = 0.0; + for (int i = 0; i < getN(values); i++) { + accum += Math.pow(values[i], 2.0); + } + return accum; + } + + public static double getMean(double[] values) { + return getSum(values) / getN(values); + } + + public static double getVariance(double[] values) { + double variance = Double.NaN; + + if (getN(values) == 1) { + variance = 0; + } else if (getN(values) > 1) { + double mean = getMean(values); + double accum = 0.0; + for (int i = 0; i < getN(values); i++) { + accum += Math.pow((values[i] - mean), 2.0); + } + variance = accum / (getN(values) - 1); + } + return variance; + } + + public static double getStandardDeviation(double[] values) { + double stdDev = Double.NaN; + if (getN(values) != 0) { + stdDev = Math.sqrt(getVariance(values)); + } + return (stdDev); + } + + public static double getMax(double[] values) { + double max = Double.NaN; + for (int i = 0; i < getN(values); i++) { + if (i == 0) { + max = values[i]; + } else { + max = Math.max(max, values[i]); + } + } + return max; + } + + public static double getMin(double[] values) { + double min = Double.NaN; + for (int i = 0; i < getN(values); i++) { + if (i == 0) { + min = values[i]; + } else { + min = Math.min(min, values[i]); + } + } + return min; + } +} \ No newline at end of file
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