001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.numbers.angle;
018
019import org.apache.commons.numbers.core.Norm;
020import org.apache.commons.numbers.core.Sum;
021
022/**
023 * Computes the cosine of the angle between two vectors.
024 */
025public final class CosAngle {
026
027    /** Private constructor. */
028    private CosAngle() {
029        // intentionally empty.
030    }
031
032    /**
033     * Computes the cosine of the angle between {@code v1} and {@code v2}.
034     *
035     * @param v1 Cartesian coordinates of the first vector.
036     * @param v2 Cartesian coordinates of the second vector.
037     * @return the cosine of the angle between the vectors.
038     * @throws IllegalArgumentException if the sizes of the input arrays are different
039     */
040    public static double value(double[] v1,
041                               double[] v2) {
042        return Sum.ofProducts(v1, v2).getAsDouble() / Norm.L2.of(v1) / Norm.L2.of(v2);
043    }
044}