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Commons Math example source code file (UnitSphereRandomVectorGenerator.java)

This example Commons Math source code file (UnitSphereRandomVectorGenerator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Math tags/keywords

mersennetwister, mersennetwister, randomgenerator, randomgenerator, randomvectorgenerator, randomvectorgenerator, unitsphererandomvectorgenerator, unitsphererandomvectorgenerator

The Commons Math UnitSphereRandomVectorGenerator.java source code

/*
 * 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.random;


/**
 * Generate random vectors isotropically located on the surface of a sphere.
 *
 * @since 2.1
 * @version $Revision: 925812 $ $Date: 2010-03-21 11:49:31 -0400 (Sun, 21 Mar 2010) $
 */

public class UnitSphereRandomVectorGenerator
    implements RandomVectorGenerator {
    /**
     * RNG used for generating the individual components of the vectors.
     */
    private final RandomGenerator rand;
    /**
     * Space dimension.
     */
    private final int dimension;

    /**
     * @param dimension Space dimension.
     * @param rand RNG for the individual components of the vectors.
     */
    public UnitSphereRandomVectorGenerator(final int dimension,
                                           final RandomGenerator rand) {
        this.dimension = dimension;
        this.rand = rand;
    }
    /**
     * Create an object that will use a default RNG ({@link MersenneTwister}),
     * in order to generate the individual components.
     *
     * @param dimension Space dimension.
     */
    public UnitSphereRandomVectorGenerator(final int dimension) {
        this(dimension, new MersenneTwister());
    }

    /** {@inheritDoc} */
    public double[] nextVector() {

        final double[] v = new double[dimension];

        double normSq;
        do {
            normSq = 0;
            for (int i = 0; i < dimension; i++) {
                final double comp = 2 * rand.nextDouble() - 1;
                v[i] = comp;
                normSq += comp * comp;
            }
        } while (normSq > 1);

        final double f = 1 / Math.sqrt(normSq);
        for (int i = 0; i < dimension; i++) {
            v[i] *= f;
        }

        return v;

    }

}

Other Commons Math examples (source code examples)

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