| /* |
| * 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.math4.neuralnet; |
| |
| import org.apache.commons.math4.neuralnet.internal.NeuralNetException; |
| |
| /** |
| * Euclidean distance measures of n-dimensional vectors. |
| * |
| * @since 4.0 |
| */ |
| public class EuclideanDistance implements DistanceMeasure { |
| /** {@inheritDoc} */ |
| @Override |
| public double applyAsDouble(double[] a, |
| double[] b) { |
| final int len = a.length; |
| if (len != b.length) { |
| throw new NeuralNetException(NeuralNetException.SIZE_MISMATCH, |
| len, b.length); |
| } |
| |
| double sum = 0; |
| for (int i = 0; i < len; i++) { |
| final double diff = a[i] - b[i]; |
| sum += diff * diff; |
| } |
| return Math.sqrt(sum); |
| } |
| } |