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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 3 of the License, or (at your |
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10 option) any 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, see |
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19 <http://www.gnu.org/licenses/>. |
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20 |
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21 */ |
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22 |
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23 #ifdef HAVE_CONFIG_H |
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24 #include <config.h> |
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25 #endif |
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26 |
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27 #include "EIG.h" |
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28 |
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29 #include "defun-dld.h" |
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30 #include "error.h" |
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31 #include "gripes.h" |
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32 #include "oct-obj.h" |
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33 #include "utils.h" |
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34 |
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35 DEFUN_DLD (eig, args, nargout, |
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36 "-*- texinfo -*-\n\ |
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37 @deftypefn {Loadable Function} {@var{lambda} =} eig (@var{a})\n\ |
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38 @deftypefnx {Loadable Function} {[@var{v}, @var{lambda}] =} eig (@var{a})\n\ |
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39 The eigenvalues (and eigenvectors) of a matrix are computed in a several\n\ |
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40 step process which begins with a Hessenberg decomposition, followed by a\n\ |
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41 Schur decomposition, from which the eigenvalues are apparent. The\n\ |
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42 eigenvectors, when desired, are computed by further manipulations of the\n\ |
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43 Schur decomposition.\n\ |
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44 \n\ |
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45 The eigenvalues returned by @code{eig} are not ordered.\n\ |
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46 @end deftypefn") |
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47 { |
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48 octave_value_list retval; |
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49 |
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50 int nargin = args.length (); |
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51 |
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52 if (nargin != 1 || nargout > 2) |
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53 { |
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54 print_usage (); |
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55 return retval; |
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56 } |
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57 |
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58 octave_value arg = args(0); |
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59 |
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60 octave_idx_type nr = arg.rows (); |
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61 octave_idx_type nc = arg.columns (); |
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62 |
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63 int arg_is_empty = empty_arg ("eig", nr, nc); |
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64 if (arg_is_empty < 0) |
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65 return retval; |
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66 else if (arg_is_empty > 0) |
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67 return octave_value_list (2, Matrix ()); |
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68 |
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69 if (nr != nc) |
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70 { |
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71 gripe_square_matrix_required ("eig"); |
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72 return retval; |
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73 } |
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74 |
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75 Matrix tmp; |
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76 ComplexMatrix ctmp; |
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77 EIG result; |
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78 |
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79 if (arg.is_real_type ()) |
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80 { |
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81 tmp = arg.matrix_value (); |
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82 |
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83 if (error_state) |
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84 return retval; |
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85 else |
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86 result = EIG (tmp, nargout > 1); |
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87 } |
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88 else if (arg.is_complex_type ()) |
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89 { |
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90 ctmp = arg.complex_matrix_value (); |
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91 |
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92 if (error_state) |
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93 return retval; |
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94 else |
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95 result = EIG (ctmp, nargout > 1); |
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96 } |
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97 else |
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98 { |
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99 gripe_wrong_type_arg ("eig", tmp); |
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100 return retval; |
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101 } |
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102 |
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103 if (nargout == 0 || nargout == 1) |
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104 { |
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105 retval(0) = result.eigenvalues (); |
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106 } |
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107 else |
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108 { |
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109 // Blame it on Matlab. |
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110 |
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111 ComplexDiagMatrix d (result.eigenvalues ()); |
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112 |
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113 retval(1) = d; |
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114 retval(0) = result.eigenvectors (); |
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115 } |
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116 |
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117 return retval; |
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118 } |
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119 |
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120 /* |
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121 ;;; Local Variables: *** |
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122 ;;; mode: C++ *** |
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123 ;;; End: *** |
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124 */ |
