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.rng.sampling.distribution; 018 019/** 020 * Sampling from a log-normal distribution. 021 * 022 * @since 1.1 023 */ 024public class LogNormalSampler implements ContinuousSampler { 025 /** Scale. */ 026 private final double scale; 027 /** Shape. */ 028 private final double shape; 029 /** Gaussian sampling. */ 030 private final NormalizedGaussianSampler gaussian; 031 032 /** 033 * @param gaussian N(0,1) generator. 034 * @param scale Scale of the log-normal distribution. 035 * @param shape Shape of the log-normal distribution. 036 */ 037 public LogNormalSampler(NormalizedGaussianSampler gaussian, 038 double scale, 039 double shape) { 040 this.scale = scale; 041 this.shape = shape; 042 this.gaussian = gaussian; 043 } 044 045 /** {@inheritDoc} */ 046 @Override 047 public double sample() { 048 return Math.exp(scale + shape * gaussian.sample()); 049 } 050 051 /** {@inheritDoc} */ 052 @Override 053 public String toString() { 054 return "Log-normal deviate [" + gaussian.toString() + "]"; 055 } 056}