PowerMathFunction.java

/*
 * Class:        PowerMathFunction
 * Description:  
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       Éric Buist
 * @since
 *
 *
 * Licensed 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 umontreal.ssj.functions;

public class PowerMathFunction implements MathFunction
 
      , MathFunctionWithFirstDerivative {
   private MathFunction func;
   private double a, b;
   private double power;

   public PowerMathFunction(MathFunction func, double power) {
      this(func, 1, 0, power);
   }

   public PowerMathFunction(MathFunction func, double a, double b, double power) {
      if (func == null)
         throw new NullPointerException();
      this.func = func;
      this.a = a;
      this.b = b;
      this.power = power;
   }

   public MathFunction getFunction() {
      return func;
   }

   public double getA() {
      return a;
   }

   public double getB() {
      return b;
   }

   public double getPower() {
      return power;
   }
 
   public double derivative(double x) {
      final double fder = MathFunctionUtil.derivative(func, x);
      return getA() * getPower() * Math.pow(getA() * func.evaluate(x) + getB(), getPower() - 1) * fder;
   }
 
   public double evaluate(double x) {
      final double v = func.evaluate(x);
      return Math.pow(a * v + b, power);
   }
}