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1 /* |
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2 |
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3 Copyright (C) 1996, 1997 John W. Eaton |
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4 |
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5 This file is part of Octave. |
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6 |
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7 Octave is free software; you can redistribute it and/or modify it |
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8 under the terms of the GNU General Public License as published by the |
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9 Free Software Foundation; either version 2, or (at your option) any |
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10 later version. |
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11 |
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12 Octave is distributed in the hope that it will be useful, but WITHOUT |
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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15 for more details. |
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16 |
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17 You should have received a copy of the GNU General Public License |
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18 along with Octave; see the file COPYING. If not, write to the Free |
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19 Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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20 02110-1301, USA. |
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21 |
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22 */ |
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23 |
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24 // Originally written by A. S. Hodel <scotte@eng.auburn.edu> |
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25 |
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26 #ifdef HAVE_CONFIG_H |
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27 #include <config.h> |
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28 #endif |
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29 |
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30 #include "defun-dld.h" |
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31 #include "error.h" |
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32 #include "oct-obj.h" |
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33 |
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34 DEFUN_DLD (givens, args, nargout, |
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35 "-*- texinfo -*-\n\ |
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36 @deftypefn {Loadable Function} {@var{g} =} givens (@var{x}, @var{y})\n\ |
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37 @deftypefnx {Loadable Function} {[@var{c}, @var{s}] =} givens (@var{x}, @var{y})\n\ |
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38 @iftex\n\ |
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39 @tex\n\ |
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40 Return a $2\\times 2$ orthogonal matrix\n\ |
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41 $$\n\ |
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42 G = \\left[\\matrix{c & s\\cr -s'& c\\cr}\\right]\n\ |
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43 $$\n\ |
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44 such that\n\ |
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45 $$\n\ |
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46 G \\left[\\matrix{x\\cr y}\\right] = \\left[\\matrix{\\ast\\cr 0}\\right]\n\ |
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47 $$\n\ |
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48 with $x$ and $y$ scalars.\n\ |
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49 @end tex\n\ |
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50 @end iftex\n\ |
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51 @ifinfo\n\ |
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52 Return a 2 by 2 orthogonal matrix\n\ |
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53 @code{@var{g} = [@var{c} @var{s}; -@var{s}' @var{c}]} such that\n\ |
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54 @code{@var{g} [@var{x}; @var{y}] = [*; 0]} with @var{x} and @var{y} scalars.\n\ |
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55 @end ifinfo\n\ |
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56 \n\ |
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57 For example,\n\ |
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58 \n\ |
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59 @example\n\ |
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60 @group\n\ |
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61 givens (1, 1)\n\ |
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62 @result{} 0.70711 0.70711\n\ |
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63 -0.70711 0.70711\n\ |
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64 @end group\n\ |
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65 @end example\n\ |
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66 @end deftypefn") |
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67 { |
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68 octave_value_list retval; |
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69 |
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70 int nargin = args.length (); |
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71 |
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72 if (nargin != 2 || nargout > 2) |
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73 { |
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74 print_usage (); |
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75 return retval; |
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76 } |
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77 else |
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78 { |
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79 if (args(0).is_complex_type () || args(1).is_complex_type ()) |
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80 { |
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81 Complex cx = args(0).complex_value (); |
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82 Complex cy = args(1).complex_value (); |
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83 |
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84 if (! error_state) |
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85 { |
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86 ComplexMatrix result = Givens (cx, cy); |
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87 |
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88 if (! error_state) |
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89 { |
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90 switch (nargout) |
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91 { |
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92 case 0: |
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93 case 1: |
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94 retval(0) = result; |
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95 break; |
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96 |
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97 case 2: |
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98 retval(1) = result (0, 1); |
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99 retval(0) = result (0, 0); |
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100 break; |
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101 |
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102 default: |
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103 error ("givens: invalid number of output arguments"); |
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104 break; |
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105 } |
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106 } |
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107 } |
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108 } |
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109 else |
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110 { |
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111 double x = args(0).double_value (); |
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112 double y = args(1).double_value (); |
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113 |
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114 if (! error_state) |
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115 { |
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116 Matrix result = Givens (x, y); |
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117 |
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118 if (! error_state) |
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119 { |
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120 switch (nargout) |
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121 { |
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122 case 0: |
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123 case 1: |
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124 retval(0) = result; |
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125 break; |
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126 |
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127 case 2: |
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128 retval(1) = result (0, 1); |
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129 retval(0) = result (0, 0); |
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130 break; |
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131 |
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132 default: |
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133 error ("givens: invalid number of output arguments"); |
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134 break; |
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135 } |
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136 } |
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137 } |
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138 } |
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139 } |
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140 |
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141 return retval; |
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142 } |
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143 |
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144 /* |
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145 ;;; Local Variables: *** |
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146 ;;; mode: C++ *** |
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147 ;;; End: *** |
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148 */ |
