| /* |
| * 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.optimization.fitting; |
| |
| import java.io.Serializable; |
| |
| import org.apache.commons.math.analysis.DifferentiableUnivariateRealFunction; |
| import org.apache.commons.math.analysis.UnivariateRealFunction; |
| import org.apache.commons.math.exception.DimensionMismatchException; |
| import org.apache.commons.math.exception.util.LocalizedFormats; |
| import org.apache.commons.math.exception.ZeroException; |
| import org.apache.commons.math.exception.NullArgumentException; |
| |
| /** |
| * A Gaussian function. Specifically: |
| * <p> |
| * <tt>f(x) = a + b*exp(-((x - c)^2 / (2*d^2)))</tt> |
| * <p> |
| * Notation key: |
| * <ul> |
| * <li><tt>x^n</tt>: <tt>x</tt> raised to the power of <tt>n</tt> |
| * <li><tt>exp(x)</tt>: <i>e</i><tt>^x</tt> |
| * </ul> |
| * References: |
| * <ul> |
| * <li><a href="http://en.wikipedia.org/wiki/Gaussian_function">Wikipedia: |
| * Gaussian function</a> |
| * </ul> |
| * |
| * @see GaussianDerivativeFunction |
| * @see ParametricGaussianFunction |
| * @since 2.2 |
| * @version $Revision: 1037327 $ $Date: 2010-11-20 21:57:37 +0100 (sam. 20 nov. 2010) $ |
| */ |
| public class GaussianFunction implements DifferentiableUnivariateRealFunction, Serializable { |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = -3195385616125629512L; |
| |
| /** Parameter a of this function. */ |
| private final double a; |
| |
| /** Parameter b of this function. */ |
| private final double b; |
| |
| /** Parameter c of this function. */ |
| private final double c; |
| |
| /** Parameter d of this function. */ |
| private final double d; |
| |
| /** |
| * Constructs an instance with the specified parameters. |
| * |
| * @param a <tt>a</tt> parameter value |
| * @param b <tt>b</tt> parameter value |
| * @param c <tt>c</tt> parameter value |
| * @param d <tt>d</tt> parameter value |
| * |
| * @throws IllegalArgumentException if <code>d</code> is 0 |
| */ |
| public GaussianFunction(double a, double b, double c, double d) { |
| if (d == 0.0) { |
| throw new ZeroException(); |
| } |
| this.a = a; |
| this.b = b; |
| this.c = c; |
| this.d = d; |
| } |
| |
| /** |
| * Constructs an instance with the specified parameters. |
| * |
| * @param parameters <tt>a</tt>, <tt>b</tt>, <tt>c</tt>, and <tt>d</tt> |
| * parameter values |
| * |
| * @throws IllegalArgumentException if <code>parameters</code> is null, |
| * <code>parameters</code> length is not 4, or if |
| * <code>parameters[3]</code> is 0 |
| */ |
| public GaussianFunction(double[] parameters) { |
| if (parameters == null) { |
| throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY); |
| } |
| if (parameters.length != 4) { |
| throw new DimensionMismatchException(4, parameters.length); |
| } |
| if (parameters[3] == 0.0) { |
| throw new ZeroException(); |
| } |
| this.a = parameters[0]; |
| this.b = parameters[1]; |
| this.c = parameters[2]; |
| this.d = parameters[3]; |
| } |
| |
| /** {@inheritDoc} */ |
| public UnivariateRealFunction derivative() { |
| return new GaussianDerivativeFunction(b, c, d); |
| } |
| |
| /** {@inheritDoc} */ |
| public double value(double x) { |
| final double xMc = x - c; |
| return a + b * Math.exp(-xMc * xMc / (2.0 * (d * d))); |
| } |
| |
| /** |
| * Gets <tt>a</tt> parameter value. |
| * |
| * @return <tt>a</tt> parameter value |
| */ |
| public double getA() { |
| return a; |
| } |
| |
| /** |
| * Gets <tt>b</tt> parameter value. |
| * |
| * @return <tt>b</tt> parameter value |
| */ |
| public double getB() { |
| return b; |
| } |
| |
| /** |
| * Gets <tt>c</tt> parameter value. |
| * |
| * @return <tt>c</tt> parameter value |
| */ |
| public double getC() { |
| return c; |
| } |
| |
| /** |
| * Gets <tt>d</tt> parameter value. |
| * |
| * @return <tt>d</tt> parameter value |
| */ |
| public double getD() { |
| return d; |
| } |
| } |