1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.rng.sampling.distribution; 18 19 /** 20 * Sampling from a log-normal distribution. 21 * 22 * @since 1.1 23 */ 24 public class LogNormalSampler implements ContinuousSampler { 25 /** Scale. */ 26 private final double scale; 27 /** Shape. */ 28 private final double shape; 29 /** Gaussian sampling. */ 30 private final NormalizedGaussianSampler gaussian; 31 32 /** 33 * @param gaussian N(0,1) generator. 34 * @param scale Scale of the log-normal distribution. 35 * @param shape Shape of the log-normal distribution. 36 */ 37 public LogNormalSampler(NormalizedGaussianSampler gaussian, 38 double scale, 39 double shape) { 40 this.scale = scale; 41 this.shape = shape; 42 this.gaussian = gaussian; 43 } 44 45 /** {@inheritDoc} */ 46 @Override 47 public double sample() { 48 return Math.exp(scale + shape * gaussian.sample()); 49 } 50 51 /** {@inheritDoc} */ 52 @Override 53 public String toString() { 54 return "Log-normal deviate [" + gaussian.toString() + "]"; 55 } 56 }