AverageMathFunction.java

/*
 * Class:        AverageMathFunction
 * 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 AverageMathFunction implements MathFunction
 
      , MathFunctionWithFirstDerivative, MathFunctionWithDerivative, MathFunctionWithIntegral {
   private MathFunction[] func;

   public AverageMathFunction(MathFunction... func) {
      if (func == null)
         throw new NullPointerException();
      this.func = func.clone();
   }

   public MathFunction[] getFunctions() {
      return func.clone();
   }
 
   public double evaluate(double x) {
      double sum = 0;
      for (final MathFunction fi : func)
         sum += fi.evaluate(x);
      return sum / func.length;
   }
 
   public double derivative(double x, int n) {
      if (n < 0)
         throw new IllegalArgumentException("n must be greater than or equal to 0");
      if (n == 0)
         return evaluate(x);
      double sum = 0;
      for (final MathFunction fi : func)
         sum += MathFunctionUtil.derivative(fi, x, n);
      return sum / func.length;
   }
 
   public double derivative(double x) {
      double sum = 0;
      for (final MathFunction fi : func)
         sum += MathFunctionUtil.derivative(fi, x);
      return sum / func.length;
   }
 
   public double integral(double a, double b) {
      double sum = 0;
      for (final MathFunction fi : func)
         sum += MathFunctionUtil.integral(fi, a, b);
      return sum / func.length;
   }
}