001 /* 002 * Copyright (C) 2008-2010 by Holger Arndt 003 * 004 * This file is part of the Universal Java Matrix Package (UJMP). 005 * See the NOTICE file distributed with this work for additional 006 * information regarding copyright ownership and licensing. 007 * 008 * UJMP is free software; you can redistribute it and/or modify 009 * it under the terms of the GNU Lesser General Public License as 010 * published by the Free Software Foundation; either version 2 011 * of the License, or (at your option) any later version. 012 * 013 * UJMP is distributed in the hope that it will be useful, 014 * but WITHOUT ANY WARRANTY; without even the implied warranty of 015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 016 * GNU Lesser General Public License for more details. 017 * 018 * You should have received a copy of the GNU Lesser General Public 019 * License along with UJMP; if not, write to the 020 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, 021 * Boston, MA 02110-1301 USA 022 */ 023 024 package org.ujmp.core.util; 025 026 /** 027 * This distance measure yields the <i>euclidian distance</i> between two 028 * samples of <code>double</code> values. 029 */ 030 public class EuclidianDistance implements DistanceMeasure { 031 032 /** 033 * Get the distance between two data samples. 034 * 035 * @param sample1 036 * the first sample of <code>double</code> values 037 * @param sample2 038 * the second sample of <code>double</code> values 039 * @return the distance between <code>sample1</code> and 040 * <code>sample2</code> 041 * @throws IllegalArgumentException 042 * if the two samples contain different amounts of values 043 */ 044 public double getDistance(double[] sample1, double[] sample2) throws IllegalArgumentException { 045 046 int n = sample1.length; 047 if (n != sample2.length || n < 1) 048 throw new IllegalArgumentException("Input arrays must have the same length."); 049 050 double sumOfSquares = 0; 051 for (int i = 0; i < n; i++) { 052 if (Double.isNaN(sample1[i]) || Double.isNaN(sample2[i])) 053 continue; 054 055 sumOfSquares += (sample1[i] - sample2[i]) * (sample1[i] - sample2[i]); 056 } 057 058 return Math.sqrt(sumOfSquares); 059 } 060 }