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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 #ifdef HAVE_CONFIG_H |
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25 #include <config.h> |
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26 #endif |
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27 |
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28 #include "CmplxLU.h" |
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29 #include "dbleLU.h" |
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30 |
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31 #include "defun-dld.h" |
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32 #include "error.h" |
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33 #include "gripes.h" |
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34 #include "oct-obj.h" |
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35 #include "utils.h" |
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36 |
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37 DEFUN_DLD (lu, args, nargout, |
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38 "-*- texinfo -*-\n\ |
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39 @deftypefn {Loadable Function} {[@var{l}, @var{u}, @var{p}] =} lu (@var{a})\n\ |
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40 @cindex LU decomposition\n\ |
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41 Compute the LU decomposition of @var{a}, using subroutines from\n\ |
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42 @sc{Lapack}. The result is returned in a permuted form, according to\n\ |
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43 the optional return value @var{p}. For example, given the matrix\n\ |
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44 @code{a = [1, 2; 3, 4]},\n\ |
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45 \n\ |
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46 @example\n\ |
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47 [l, u, p] = lu (a)\n\ |
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48 @end example\n\ |
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49 \n\ |
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50 @noindent\n\ |
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51 returns\n\ |
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52 \n\ |
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53 @example\n\ |
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54 l =\n\ |
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55 \n\ |
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56 1.00000 0.00000\n\ |
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57 0.33333 1.00000\n\ |
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58 \n\ |
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59 u =\n\ |
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60 \n\ |
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61 3.00000 4.00000\n\ |
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62 0.00000 0.66667\n\ |
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63 \n\ |
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64 p =\n\ |
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65 \n\ |
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66 0 1\n\ |
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67 1 0\n\ |
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68 @end example\n\ |
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69 \n\ |
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70 The matrix is not required to be square.\n\ |
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71 @end deftypefn") |
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72 { |
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73 octave_value_list retval; |
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74 |
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75 int nargin = args.length (); |
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76 |
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77 if (nargin != 1 || nargout > 3) |
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78 { |
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79 print_usage ("lu"); |
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80 return retval; |
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81 } |
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82 |
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83 octave_value arg = args(0); |
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84 |
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85 octave_idx_type nr = arg.rows (); |
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86 octave_idx_type nc = arg.columns (); |
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87 |
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88 int arg_is_empty = empty_arg ("lu", nr, nc); |
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89 |
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90 if (arg_is_empty < 0) |
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91 return retval; |
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92 else if (arg_is_empty > 0) |
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93 return octave_value_list (3, Matrix ()); |
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94 |
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95 if (arg.is_real_type ()) |
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96 { |
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97 Matrix m = arg.matrix_value (); |
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98 |
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99 if (! error_state) |
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100 { |
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101 LU fact (m); |
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102 |
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103 switch (nargout) |
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104 { |
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105 case 0: |
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106 case 1: |
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107 case 2: |
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108 { |
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109 Matrix P = fact.P (); |
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110 Matrix L = P.transpose () * fact.L (); |
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111 retval(1) = fact.U (); |
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112 retval(0) = L; |
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113 } |
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114 break; |
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115 |
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116 case 3: |
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117 default: |
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118 retval(2) = fact.P (); |
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119 retval(1) = fact.U (); |
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120 retval(0) = fact.L (); |
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121 break; |
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122 } |
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123 } |
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124 } |
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125 else if (arg.is_complex_type ()) |
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126 { |
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127 ComplexMatrix m = arg.complex_matrix_value (); |
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128 |
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129 if (! error_state) |
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130 { |
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131 ComplexLU fact (m); |
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132 |
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133 switch (nargout) |
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134 { |
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135 case 0: |
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136 case 1: |
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137 case 2: |
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138 { |
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139 Matrix P = fact.P (); |
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140 ComplexMatrix L = P.transpose () * fact.L (); |
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141 retval(1) = fact.U (); |
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142 retval(0) = L; |
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143 } |
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144 break; |
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145 |
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146 case 3: |
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147 default: |
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148 retval(2) = fact.P (); |
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149 retval(1) = fact.U (); |
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150 retval(0) = fact.L (); |
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151 break; |
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152 } |
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153 } |
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154 } |
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155 else |
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156 { |
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157 gripe_wrong_type_arg ("lu", arg); |
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158 } |
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159 |
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160 return retval; |
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161 } |
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162 |
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163 /* |
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164 ;;; Local Variables: *** |
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165 ;;; mode: C++ *** |
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166 ;;; End: *** |
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167 */ |
