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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 "quit.h" |
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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 "gripes.h" |
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33 #include "oct-obj.h" |
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34 |
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35 // Find at most N_TO_FIND nonzero elements in NDA. Search forward if |
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36 // DIRECTION is 1, backward if it is -1. NARGOUT is the number of |
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37 // output arguments. If N_TO_FIND is -1, find all nonzero elements. |
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38 |
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39 template <typename T> |
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40 octave_value_list |
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41 find_nonzero_elem_idx (const T& nda, int nargout, octave_idx_type n_to_find, |
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42 int direction) |
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43 { |
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44 octave_value_list retval ((nargout == 0 ? 1 : nargout), Matrix ()); |
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45 |
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46 octave_idx_type count = 0; |
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47 |
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48 octave_idx_type nel = nda.nelem (); |
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49 |
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50 // Set the starting element to the correct value based on the |
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51 // direction to search. |
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52 octave_idx_type k = 0; |
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53 if (direction == -1) |
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54 k = nel - 1; |
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55 |
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56 // Search in the default range. |
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57 octave_idx_type start_el = -1; |
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58 octave_idx_type end_el = -1; |
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59 |
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60 // Search for the number of elements to return. |
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61 while (k < nel && k > -1 && n_to_find != count) |
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62 { |
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63 OCTAVE_QUIT; |
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64 |
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65 if (nda(k) != 0.0) |
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66 { |
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67 end_el = k; |
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68 if (start_el == -1) |
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69 start_el = k; |
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70 count++; |
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71 } |
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72 k = k + direction; |
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73 } |
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74 |
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75 // Reverse the range if we're looking backward. |
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76 if (direction == -1) |
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77 { |
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78 octave_idx_type tmp_el = start_el; |
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79 start_el = end_el; |
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80 end_el = tmp_el; |
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81 } |
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82 // Fix an off by one error. |
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83 end_el++; |
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84 |
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85 // If the original argument was a row vector, force a row vector of |
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86 // the overall indices to be returned. But see below for scalar |
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87 // case... |
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88 |
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89 octave_idx_type result_nr = count; |
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90 octave_idx_type result_nc = 1; |
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91 |
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92 bool scalar_arg = false; |
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93 |
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94 if (nda.ndims () == 2 && nda.rows () == 1) |
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95 { |
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96 result_nr = 1; |
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97 result_nc = count; |
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98 |
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99 scalar_arg = (nda.columns () == 1); |
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100 } |
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101 |
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102 Matrix idx (result_nr, result_nc); |
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103 |
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104 Matrix i_idx (result_nr, result_nc); |
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105 Matrix j_idx (result_nr, result_nc); |
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106 |
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107 T val (dim_vector (result_nr, result_nc)); |
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108 |
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109 if (count > 0) |
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110 { |
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111 count = 0; |
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112 |
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113 octave_idx_type nr = nda.rows (); |
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114 |
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115 octave_idx_type i = 0; |
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116 octave_idx_type j = 0; |
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117 |
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118 // Search for elements to return. Only search the region where |
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119 // there are elements to be found using the count that we want |
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120 // to find. |
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121 for (k = start_el; k < end_el; k++) |
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122 { |
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123 OCTAVE_QUIT; |
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124 |
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125 if (nda(k) != 0.0) |
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126 { |
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127 idx(count) = k + 1; |
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128 |
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129 i_idx(count) = i + 1; |
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130 j_idx(count) = j + 1; |
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131 |
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132 val(count) = nda(k); |
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133 |
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134 count++; |
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135 } |
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136 |
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137 i++; |
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138 |
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139 if (i == nr) |
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140 { |
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141 i = 0; |
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142 |
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143 j++; |
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144 } |
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145 } |
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146 } |
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147 else if (scalar_arg) |
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148 { |
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149 idx.resize (0, 0); |
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150 |
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151 i_idx.resize (0, 0); |
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152 j_idx.resize (0, 0); |
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153 |
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154 val.resize (dim_vector (0, 0)); |
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155 } |
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156 |
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157 switch (nargout) |
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158 { |
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159 case 0: |
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160 case 1: |
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161 retval(0) = idx; |
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162 break; |
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163 |
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164 case 3: |
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165 retval(2) = val; |
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166 // Fall through! |
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167 |
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168 case 2: |
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169 retval(1) = j_idx; |
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170 retval(0) = i_idx; |
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171 break; |
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172 |
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173 default: |
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174 panic_impossible (); |
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175 break; |
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176 } |
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177 |
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178 return retval; |
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179 } |
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180 |
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181 template octave_value_list find_nonzero_elem_idx (const NDArray&, int, |
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182 octave_idx_type, int); |
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183 |
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184 template octave_value_list find_nonzero_elem_idx (const ComplexNDArray&, int, |
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185 octave_idx_type, int); |
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186 |
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187 DEFUN_DLD (find, args, nargout, |
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188 "-*- texinfo -*-\n\ |
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189 @deftypefn {Loadable Function} {} find (@var{x})\n\ |
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190 @deftypefnx {Loadable Function} {} find (@var{x}, @var{n})\n\ |
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191 @deftypefnx {Loadable Function} {} find (@var{x}, @var{n}, @var{direction})\n\ |
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192 Return a vector of indices of nonzero elements of a matrix. To obtain a\n\ |
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193 single index for each matrix element, Octave pretends that the columns\n\ |
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194 of a matrix form one long vector (like Fortran arrays are stored). For\n\ |
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195 example,\n\ |
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196 \n\ |
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197 @example\n\ |
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198 @group\n\ |
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199 find (eye (2))\n\ |
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200 @result{} [ 1; 4 ]\n\ |
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201 @end group\n\ |
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202 @end example\n\ |
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203 \n\ |
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204 If two outputs are requested, @code{find} returns the row and column\n\ |
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205 indices of nonzero elements of a matrix. For example,\n\ |
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206 \n\ |
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207 @example\n\ |
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208 @group\n\ |
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209 [i, j] = find (2 * eye (2))\n\ |
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210 @result{} i = [ 1; 2 ]\n\ |
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211 @result{} j = [ 1; 2 ]\n\ |
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212 @end group\n\ |
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213 @end example\n\ |
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214 \n\ |
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215 If three outputs are requested, @code{find} also returns a vector\n\ |
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216 containing the nonzero values. For example,\n\ |
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217 \n\ |
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218 @example\n\ |
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219 @group\n\ |
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220 [i, j, v] = find (3 * eye (2))\n\ |
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221 @result{} i = [ 1; 2 ]\n\ |
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222 @result{} j = [ 1; 2 ]\n\ |
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223 @result{} v = [ 3; 3 ]\n\ |
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224 @end group\n\ |
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225 @end example\n\ |
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226 \n\ |
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227 If two inputs are given, @var{n} indicates the number of elements to\n\ |
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228 find from the beginning of the matrix or vector.\n\ |
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229 \n\ |
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230 If three inputs are given, @var{direction} should be one of \"first\" or\n\ |
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231 \"last\" indicating that it should start counting found elements from the\n\ |
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232 first or last element.\n\ |
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233 @end deftypefn") |
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234 { |
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235 octave_value_list retval; |
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236 |
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237 int nargin = args.length (); |
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238 |
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239 if (nargin > 3 || nargin < 1) |
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240 { |
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241 print_usage (); |
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242 return retval; |
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243 } |
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244 |
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245 // Setup the default options. |
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246 octave_idx_type n_to_find = -1; |
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247 if (nargin > 1) |
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248 { |
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249 n_to_find = args(1).int_value (); |
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250 if (error_state) |
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251 { |
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252 error ("find: expecting second argument to be an integer"); |
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253 return retval; |
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254 } |
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255 } |
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256 |
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257 // Direction to do the searching (1 == forward, -1 == reverse). |
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258 int direction = 1; |
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259 if (nargin > 2) |
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260 { |
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261 direction = 0; |
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262 |
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263 std::string s_arg = args(2).string_value (); |
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264 |
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265 if (! error_state) |
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266 { |
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267 if (s_arg == "first") |
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268 direction = 1; |
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269 else if (s_arg == "last") |
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270 direction = -1; |
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271 } |
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272 |
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273 if (direction == 0) |
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274 { |
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275 error ("find: expecting third argument to be \"first\" or \"last\""); |
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276 return retval; |
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277 } |
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278 } |
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279 |
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280 octave_value arg = args(0); |
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281 |
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282 if (arg.is_real_type ()) |
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283 { |
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284 NDArray nda = arg.array_value (); |
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285 |
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286 if (! error_state) |
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287 retval = find_nonzero_elem_idx (nda, nargout, n_to_find, direction); |
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288 } |
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289 else if (arg.is_complex_type ()) |
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290 { |
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291 ComplexNDArray cnda = arg.complex_array_value (); |
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292 |
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293 if (! error_state) |
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294 retval = find_nonzero_elem_idx (cnda, nargout, n_to_find, direction); |
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295 } |
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296 else if (arg.is_string ()) |
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297 { |
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298 charNDArray cnda = arg.char_array_value (); |
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299 |
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300 if (! error_state) |
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301 retval = find_nonzero_elem_idx (cnda, nargout, n_to_find, direction); |
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302 } |
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303 else |
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304 { |
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305 gripe_wrong_type_arg ("find", arg); |
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306 } |
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307 |
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308 return retval; |
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309 } |
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310 |
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311 /* |
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312 ;;; Local Variables: *** |
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313 ;;; mode: C++ *** |
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314 ;;; End: *** |
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315 */ |
