001/*
002 * $Id: MathUtils.java,v 1.4 2011/03/24 16:06:33 davep Exp $
003 *
004 * This file is part of McIDAS-V
005 *
006 * Copyright 2007-2011
007 * Space Science and Engineering Center (SSEC)
008 * University of Wisconsin - Madison
009 * 1225 W. Dayton Street, Madison, WI 53706, USA
010 * https://www.ssec.wisc.edu/mcidas
011 * 
012 * All Rights Reserved
013 * 
014 * McIDAS-V is built on Unidata's IDV and SSEC's VisAD libraries, and
015 * some McIDAS-V source code is based on IDV and VisAD source code.  
016 * 
017 * McIDAS-V is free software; you can redistribute it and/or modify
018 * it under the terms of the GNU Lesser Public License as published by
019 * the Free Software Foundation; either version 3 of the License, or
020 * (at your option) any later version.
021 * 
022 * McIDAS-V is distributed in the hope that it will be useful,
023 * but WITHOUT ANY WARRANTY; without even the implied warranty of
024 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
025 * GNU Lesser Public License for more details.
026 * 
027 * You should have received a copy of the GNU Lesser Public License
028 * along with this program.  If not, see http://www.gnu.org/licenses.
029 */
030// Shawn E. Gano
031/**
032 * =====================================================================
033 * Copyright (C) 2009 Shawn E. Gano
034 * 
035 * This file is part of JSatTrak.
036 * 
037 * JSatTrak is free software: you can redistribute it and/or modify
038 * it under the terms of the GNU Lesser General Public License as published by
039 * the Free Software Foundation, either version 3 of the License, or
040 * (at your option) any later version.
041 * 
042 * JSatTrak is distributed in the hope that it will be useful,
043 * but WITHOUT ANY WARRANTY; without even the implied warranty of
044 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
045 * GNU Lesser General Public License for more details.
046 * 
047 * You should have received a copy of the GNU Lesser General Public License
048 * along with JSatTrak.  If not, see <http://www.gnu.org/licenses/>.
049 * =====================================================================
050 */
051
052package edu.wisc.ssec.mcidasv.data.adde.sgp4;
053
054/**
055 * Various Math functions; many of them for vector and matrix operations for 3 dimensions.
056 */
057public class MathUtils
058{
059
060//      vector 2-norm
061    /**
062     * vector 2-norm
063     *
064     * @param a vector of length 3
065     * @return norm(a)
066     */
067        public static double norm(double[] a)
068        {
069                double c = 0.0;
070
071                for(int i=0;i<a.length;i++)
072                {
073                        c += a[i]*a[i];
074                }
075
076                return Math.sqrt(c);
077        }
078
079        // dot product for 3D vectors
080    /**
081     * dot product for 3D vectors
082     *
083     * @param a 3x1 vector
084     * @param b 3x1 vector
085     * @return a dot b
086     */
087        public static double dot(double[] a, double[] b)
088        {
089                double c =0;;
090
091                for (int i = 0; i < 3; i++) // row
092                {
093                        c += a[i]*b[i];
094                }
095
096                return c;
097
098        } // mult 3x3 matrices
099
100    /**
101     * multiply two matrices 3x3
102     *
103     * @param a 3x3 matrix
104     * @param b 3x3 matrix
105     * @return a x b
106     */
107        public static double[][] mult(double[][] a, double[][] b)
108        {
109                double[][] c = new double[3][3];
110
111                for (int i = 0; i < 3; i++) // row
112                {
113                        for (int j = 0; j < 3; j++) // col
114                        {
115                                c[i][j] = 0.0;
116                                for (int k = 0; k < 3; k++)
117                                {
118                                        c[i][j] += a[i][k] * b[k][j];
119                                }
120                        }
121                }
122
123                return c;
124
125        } // mult 3x3 matrices
126
127    /**
128     * vector subtraction
129     *
130     * @param a vector of length 3
131     * @param b vector of length 3
132     * @return a-b
133     */
134        public static double[] sub(double[] a, double[] b)
135        {
136                double[] c = new double[3];
137                for(int i=0;i<3;i++)
138                {
139                        c[i] = a[i] - b[i];
140                }
141
142                return c;
143        }
144}