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1 ## Copyright (C) 2000, 2005, 2006, 2007 Paul Kienzle |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} [@var{bool}, @var{index}] = ismember (@var{a}, @var{s}) |
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21 ## Return a matrix @var{bool} the same shape as @var{a} which has 1 if |
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22 ## @code{a(i,j)} is in @var{s} or 0 if it isn't. If a second output argument |
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23 ## is requested, the indexes into @var{s} of the matching elements is |
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24 ## also returned. |
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25 ## @seealso{unique, union, intersection, setxor, setdiff} |
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26 ## @end deftypefn |
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27 |
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28 ## Author: Paul Kienzle |
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29 ## Adapted-by: jwe |
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30 |
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31 function [c, index] = ismember (a, s) |
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32 |
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33 if (nargin != 2) |
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34 print_usage (); |
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35 endif |
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36 |
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37 ## Convert char matrices to cell arrays. |
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38 if (ischar (a)) |
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39 a = cellstr (a); |
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40 endif |
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41 if (ischar (s)) |
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42 s = cellstr (s); |
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43 endif |
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44 |
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45 ## Input checking. |
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46 if (! isa (a, class (s))) |
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47 error ("ismember: both input arguments must be the same type"); |
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48 endif |
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49 |
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50 if (iscell (a) && ! iscellstr (a)) |
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51 error ("ismember: cell arrays may only contain strings"); |
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52 endif |
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53 |
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54 if (! isnumeric(a) && ! iscell (a)) |
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55 error ("ismember: input arguments must be arrays, cell arrays, or strings"); |
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56 endif |
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57 |
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58 ## Do the actual work. |
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59 if (isempty (a) || isempty (s)) |
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60 c = zeros (size (a), "logical"); |
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61 else |
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62 if (numel (s) == 1) |
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63 if (iscell (a)) |
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64 c = strcmp (a, s); |
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65 else |
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66 ## Both A and S are matrices. |
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67 c = (a == s); |
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68 endif |
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69 index = double (c); |
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70 elseif (numel (a) == 1) |
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71 if (iscell (a)) |
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72 f = find (strcmp (a, s), 1); |
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73 else |
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74 ## Both A and S are matrices. |
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75 f = find (a == s, 1); |
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76 endif |
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77 c = ! isempty (f); |
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78 index = f; |
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79 if (isempty (index)) |
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80 index = 0; |
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81 endif |
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82 else |
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83 ## Magic: the following code determines for each a, the index i |
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84 ## such that S(i)<= a < S(i+1). It does this by sorting the a |
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85 ## into S and remembering the source index where each element came |
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86 ## from. Since all the a's originally came after all the S's, if |
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87 ## the source index is less than the length of S, then the element |
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88 ## came from S. We can then do a cumulative sum on the indices to |
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89 ## figure out which element of S each a comes after. |
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90 ## E.g., S=[2 4 6], a=[1 2 3 4 5 6 7] |
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91 ## unsorted [S a] = [ 2 4 6 1 2 3 4 5 6 7 ] |
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92 ## sorted [ S a ] = [ 1 2 2 3 4 4 5 6 6 7 ] |
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93 ## source index p = [ 4 1 5 6 2 7 8 3 9 10 ] |
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94 ## boolean p<=l(S) = [ 0 1 0 0 1 0 0 1 0 0 ] |
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95 ## cumsum(p<=l(S)) = [ 0 1 1 1 2 2 2 3 3 3 ] |
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96 ## Note that this leaves a(1) coming after S(0) which doesn't |
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97 ## exist. So arbitrarily, we will dump all elements less than |
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98 ## S(1) into the interval after S(1). We do this by dropping S(1) |
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99 ## from the sort! E.g., S=[2 4 6], a=[1 2 3 4 5 6 7] |
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100 ## unsorted [S(2:3) a] =[4 6 1 2 3 4 5 6 7 ] |
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101 ## sorted [S(2:3) a] = [ 1 2 3 4 4 5 6 6 7 ] |
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102 ## source index p = [ 3 4 5 1 6 7 2 8 9 ] |
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103 ## boolean p<=l(S)-1 = [ 0 0 0 1 0 0 1 0 0 ] |
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104 ## cumsum(p<=l(S)-1) = [ 0 0 0 1 1 1 2 2 2 ] |
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105 ## Now we can use Octave's lvalue indexing to "invert" the sort, |
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106 ## and assign all these indices back to the appropriate A and S, |
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107 ## giving S_idx = [ -- 1 2], a_idx = [ 0 0 0 1 1 2 2 ]. Add 1 to |
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108 ## a_idx, and we know which interval S(i) contains a. It is |
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109 ## easy to now check membership by comparing S(a_idx) == a. This |
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110 ## magic works because S starts out sorted, and because sort |
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111 ## preserves the relative order of identical elements. |
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112 lt = length (s); |
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113 [s, sidx] = sort (s); |
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114 [v, p] = sort ([s(2:lt); a(:)]); |
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115 idx(p) = cumsum (p <= lt-1) + 1; |
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116 idx = idx(lt:end); |
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117 if (iscell (a) || iscell (s)) |
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118 c = (cellfun ("length", a) |
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119 == reshape (cellfun ("length", s(idx)), size (a))); |
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120 idx2 = find (c); |
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121 c(idx2) = all (char (a(idx2)) == char (s(idx)(idx2)), 2); |
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122 index = zeros (size (c)); |
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123 index(c) = sidx(idx(c)); |
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124 else |
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125 ## Both A and S are matrices. |
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126 c = (a == reshape (s (idx), size (a))); |
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127 index = zeros (size (c)); |
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128 index(c) = sidx(idx(c)); |
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129 endif |
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130 endif |
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131 endif |
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132 |
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133 endfunction |
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134 |
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135 %!assert (ismember ({''}, {'abc', 'def'}), false); |
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136 %!assert (ismember ('abc', {'abc', 'def'}), true); |
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137 %!assert (isempty (ismember ([], [1, 2])), true); |
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138 %!xtest assert (ismember ('', {'abc', 'def'}), false); |
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139 %!fail ('ismember ([], {1, 2})', 'error:.*'); |
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140 %!fail ('ismember ({[]}, {1, 2})', 'error:.*'); |
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141 %!assert (ismember ({'foo', 'bar'}, {'foobar'}), logical ([0, 0])) |
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142 %!assert (ismember ({'foo'}, {'foobar'}), false) |
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143 %!assert (ismember ({'bar'}, {'foobar'}), false) |
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144 %!assert (ismember ({'bar'}, {'foobar', 'bar'}), true) |
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145 %!assert (ismember ({'foo', 'bar'}, {'foobar', 'bar'}), logical ([0, 1])) |
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146 %!assert (ismember ({'xfb', 'f', 'b'}, {'fb', 'b'}), logical ([0, 0, 1])) |
