| /* |
| * 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.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; |
| |
| /** |
| * The derivative of {@link GaussianFunction}. Specifically: |
| * <p> |
| * <tt>f'(x) = (-b / (d^2)) * (x - c) * 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> |
| * |
| * @since 2.2 |
| * @version $Revision: 1037327 $ $Date: 2010-11-20 21:57:37 +0100 (sam. 20 nov. 2010) $ |
| */ |
| public class GaussianDerivativeFunction implements UnivariateRealFunction, Serializable { |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = -6500229089670174766L; |
| |
| /** Parameter b of this function. */ |
| private final double b; |
| |
| /** Parameter c of this function. */ |
| private final double c; |
| |
| /** Square of the parameter d of this function. */ |
| private final double d2; |
| |
| /** |
| * Constructs an instance with the specified parameters. |
| * |
| * @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 GaussianDerivativeFunction(double b, double c, double d) { |
| if (d == 0.0) { |
| throw new ZeroException(); |
| } |
| this.b = b; |
| this.c = c; |
| this.d2 = d * d; |
| } |
| |
| /** |
| * Constructs an instance with the specified parameters. |
| * |
| * @param parameters <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 3, or if |
| * <code>parameters[2]</code> is 0 |
| */ |
| public GaussianDerivativeFunction(double[] parameters) { |
| if (parameters == null) { |
| throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY); |
| } |
| if (parameters.length != 3) { |
| throw new DimensionMismatchException(3, parameters.length); |
| } |
| if (parameters[2] == 0.0) { |
| throw new ZeroException(); |
| } |
| this.b = parameters[0]; |
| this.c = parameters[1]; |
| this.d2 = parameters[2] * parameters[2]; |
| } |
| |
| /** {@inheritDoc} */ |
| public double value(double x) { |
| final double xMc = x - c; |
| return (-b / d2) * xMc * Math.exp(-(xMc * xMc) / (2.0 * d2)); |
| } |
| |
| } |