001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math3.analysis.interpolation;
018
019 import org.apache.commons.math3.analysis.MultivariateFunction;
020 import org.apache.commons.math3.exception.NotPositiveException;
021 import org.apache.commons.math3.exception.NotStrictlyPositiveException;
022 import org.apache.commons.math3.exception.NoDataException;
023 import org.apache.commons.math3.exception.DimensionMismatchException;
024 import org.apache.commons.math3.exception.NullArgumentException;
025 import org.apache.commons.math3.random.UnitSphereRandomVectorGenerator;
026
027 /**
028 * Interpolator that implements the algorithm described in
029 * <em>William Dudziak</em>'s
030 * <a href="http://www.dudziak.com/microsphere.pdf">MS thesis</a>.
031 *
032 * @since 2.1
033 * @version $Id: MicrosphereInterpolator.java 1379904 2012-09-01 23:54:52Z erans $
034 */
035 public class MicrosphereInterpolator
036 implements MultivariateInterpolator {
037 /**
038 * Default number of surface elements that composes the microsphere.
039 */
040 public static final int DEFAULT_MICROSPHERE_ELEMENTS = 2000;
041 /**
042 * Default exponent used the weights calculation.
043 */
044 public static final int DEFAULT_BRIGHTNESS_EXPONENT = 2;
045 /**
046 * Number of surface elements of the microsphere.
047 */
048 private final int microsphereElements;
049 /**
050 * Exponent used in the power law that computes the weights of the
051 * sample data.
052 */
053 private final int brightnessExponent;
054
055 /**
056 * Create a microsphere interpolator with default settings.
057 * Calling this constructor is equivalent to call {@link
058 * #MicrosphereInterpolator(int, int)
059 * MicrosphereInterpolator(MicrosphereInterpolator.DEFAULT_MICROSPHERE_ELEMENTS,
060 * MicrosphereInterpolator.DEFAULT_BRIGHTNESS_EXPONENT)}.
061 */
062 public MicrosphereInterpolator() {
063 this(DEFAULT_MICROSPHERE_ELEMENTS, DEFAULT_BRIGHTNESS_EXPONENT);
064 }
065
066 /** Create a microsphere interpolator.
067 * @param elements Number of surface elements of the microsphere.
068 * @param exponent Exponent used in the power law that computes the
069 * weights (distance dimming factor) of the sample data.
070 * @throws NotPositiveException if {@code exponent < 0}.
071 * @throws NotStrictlyPositiveException if {@code elements <= 0}.
072 */
073 public MicrosphereInterpolator(final int elements,
074 final int exponent)
075 throws NotPositiveException,
076 NotStrictlyPositiveException {
077 if (exponent < 0) {
078 throw new NotPositiveException(exponent);
079 }
080 if (elements <= 0) {
081 throw new NotStrictlyPositiveException(elements);
082 }
083
084 microsphereElements = elements;
085 brightnessExponent = exponent;
086 }
087
088 /**
089 * {@inheritDoc}
090 */
091 public MultivariateFunction interpolate(final double[][] xval,
092 final double[] yval)
093 throws DimensionMismatchException,
094 NoDataException,
095 NullArgumentException {
096 final UnitSphereRandomVectorGenerator rand
097 = new UnitSphereRandomVectorGenerator(xval[0].length);
098 return new MicrosphereInterpolatingFunction(xval, yval,
099 brightnessExponent,
100 microsphereElements,
101 rand);
102 }
103 }