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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one or more
      3  * contributor license agreements.  See the NOTICE file distributed with
      4  * this work for additional information regarding copyright ownership.
      5  * The ASF licenses this file to You under the Apache License, Version 2.0
      6  * (the "License"); you may not use this file except in compliance with
      7  * the License.  You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 package org.apache.commons.math.analysis.interpolation;
     18 
     19 import org.apache.commons.math.MathException;
     20 import org.apache.commons.math.analysis.MultivariateRealFunction;
     21 import org.apache.commons.math.exception.NotPositiveException;
     22 import org.apache.commons.math.exception.NotStrictlyPositiveException;
     23 import org.apache.commons.math.random.UnitSphereRandomVectorGenerator;
     24 
     25 /**
     26  * Interpolator that implements the algorithm described in
     27  * <em>William Dudziak</em>'s
     28  * <a href="http://www.dudziak.com/microsphere.pdf">MS thesis</a>.
     29  * @since 2.1
     30  *
     31  * @version $Revision: 980944 $ $Date: 2010-07-30 22:31:11 +0200 (ven. 30 juil. 2010) $
     32  */
     33 public class MicrosphereInterpolator
     34     implements MultivariateRealInterpolator {
     35 
     36     /**
     37      * Default number of surface elements that composes the microsphere.
     38      */
     39     public static final int DEFAULT_MICROSPHERE_ELEMENTS = 2000;
     40 
     41     /**
     42      * Default exponent used the weights calculation.
     43      */
     44     public static final int DEFAULT_BRIGHTNESS_EXPONENT = 2;
     45 
     46     /**
     47      * Number of surface elements of the microsphere.
     48      */
     49     private int microsphereElements;
     50 
     51     /**
     52      * Exponent used in the power law that computes the weights of the
     53      * sample data.
     54      */
     55     private int brightnessExponent;
     56 
     57     /** Create a microsphere interpolator with default settings.
     58      * <p>Calling this constructor is equivalent to call {@link
     59      * #MicrosphereInterpolator(int, int)
     60      * MicrosphereInterpolator(MicrosphereInterpolator.DEFAULT_MICROSPHERE_ELEMENTS,
     61      * MicrosphereInterpolator.DEFAULT_BRIGHTNESS_EXPONENT)}.</p>
     62      */
     63     public MicrosphereInterpolator() {
     64         this(DEFAULT_MICROSPHERE_ELEMENTS, DEFAULT_BRIGHTNESS_EXPONENT);
     65     }
     66 
     67     /** Create a microsphere interpolator.
     68      * @param microsphereElements number of surface elements of the microsphere.
     69      * @param brightnessExponent exponent used in the power law that computes the
     70      * weights of the sample data.
     71      * @throws NotPositiveException if {@code microsphereElements <= 0}
     72      * or {@code brightnessExponent < 0}.
     73      */
     74     public MicrosphereInterpolator(final int microsphereElements,
     75                                    final int brightnessExponent) {
     76         setMicropshereElements(microsphereElements);
     77         setBrightnessExponent(brightnessExponent);
     78     }
     79 
     80     /**
     81      * {@inheritDoc}
     82      */
     83     public MultivariateRealFunction interpolate(final double[][] xval,
     84                                                 final double[] yval)
     85         throws MathException, IllegalArgumentException {
     86         final UnitSphereRandomVectorGenerator rand
     87             = new UnitSphereRandomVectorGenerator(xval[0].length);
     88         return new MicrosphereInterpolatingFunction(xval, yval,
     89                                                     brightnessExponent,
     90                                                     microsphereElements,
     91                                                     rand);
     92     }
     93 
     94     /**
     95      * Set the brightness exponent.
     96      * @param exponent Exponent for computing the distance dimming
     97      * factor.
     98      * @throws NotPositiveException if {@code exponent < 0}.
     99      */
    100     public void setBrightnessExponent(final int exponent) {
    101         if (exponent < 0) {
    102             throw new NotPositiveException(exponent);
    103         }
    104         brightnessExponent = exponent;
    105     }
    106 
    107     /**
    108      * Set the number of microsphere elements.
    109      * @param elements Number of surface elements of the microsphere.
    110      * @throws NotStrictlyPositiveException if {@code elements <= 0}.
    111      */
    112     public void setMicropshereElements(final int elements) {
    113         if (elements <= 0) {
    114             throw new NotStrictlyPositiveException(elements);
    115         }
    116         microsphereElements = elements;
    117     }
    118 }
    119