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1 ## Copyright (C) 2000-2012 Paul Kienzle
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2 ## Copyright (C) 2008-2009 Jaroslav Hajek
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3 ##
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4 ## This file is part of Octave.
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5 ##
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6 ## Octave is free software; you can redistribute it and/or modify it
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7 ## under the terms of the GNU General Public License as published by
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8 ## the Free Software Foundation; either version 3 of the License, or (at
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9 ## your option) any later version.
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10 ##
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11 ## Octave is distributed in the hope that it will be useful, but
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 ## General Public License for more details.
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15 ##
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16 ## You should have received a copy of the GNU General Public License
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17 ## along with Octave; see the file COPYING. If not, see
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18 ## <http://www.gnu.org/licenses/>.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {} intersect (@var{a}, @var{b})
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22 ## @deftypefnx {Function File} {[@var{c}, @var{ia}, @var{ib}] =} intersect (@var{a}, @var{b})
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23 ##
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24 ## Return the elements in both @var{a} and @var{b}, sorted in ascending
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25 ## order. If @var{a} and @var{b} are both column vectors return a column
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26 ## vector, otherwise return a row vector.
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27 ## @var{a}, @var{b} may be cell arrays of string(s).
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28 ##
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29 ## Return index vectors @var{ia} and @var{ib} such that @code{a(ia)==c} and
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30 ## @code{b(ib)==c}.
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31 ##
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32 ## @end deftypefn
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33 ## @seealso{unique, union, setxor, setdiff, ismember}
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34
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35 function [c, ia, ib] = intersect (a, b, varargin)
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36
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37 if (nargin < 2 || nargin > 3)
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38 print_usage ();
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39 endif
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40
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41 ## [a, b] = validargs ("intersect", a, b, varargin{:});
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42
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43 if (isempty (a) || isempty (b))
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44 c = ia = ib = [];
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45 else
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46 ## form a and b into sets
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47 if (nargout > 1)
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48 [a, ja] = unique (a, varargin{:});
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49 [b, jb] = unique (b, varargin{:});
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50 else
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51 a = unique (a, varargin{:});
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52 b = unique (b, varargin{:});
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53 endif
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54
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55 if (nargin > 2)
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56 c = [a; b];
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57 [c, ic] = sortrows (c);
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58 ii = find (all (c(1:end-1,:) == c(2:end,:), 2));
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59 c = c(ii,:);
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60 len_a = rows (a);
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61 else
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62 c = [a(:); b(:)];
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63 [c, ic] = sort (c); ## [a(:);b(:)](ic) == c
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64 if (iscellstr (c))
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65 ii = find (strcmp (c(1:end-1), c(2:end)));
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66 else
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67 ii = find (c(1:end-1) == c(2:end));
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68 endif
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69 c = c(ii);
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70 len_a = length (a);
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71 endif
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72
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73 if (nargout > 1)
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74 ia = ja(ic(ii)); ## a(ia) == c
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75 ib = jb(ic(ii+1) - len_a); ## b(ib) == c
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76 endif
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77
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78 if (nargin == 2 && (size (b, 1) == 1 || size (a, 1) == 1))
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79 c = c.';
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80 endif
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81 endif
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82
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83 endfunction
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84
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85
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86 %!# Test the routine for index vectors ia and ib
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87 %!test
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88 %! a = [3 2 4 5 7 6 5 1 0 13 13];
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89 %! b = [3 5 12 1 1 7];
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90 %! [c,ia,ib] = intersect(a,b);
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91 %! assert(c,[1 3 5 7]);
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92 %! assert(ia,[8 1 7 5]);
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93 %! assert(ib,[5 1 2 6]);
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94 %! assert(a(ia),c);
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95 %! assert(b(ib),c);
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96 %!test
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97 %! a = [1,1,2;1,4,5;2,1,7];
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98 %! b = [1,4,5;2,3,4;1,1,2;9,8,7];
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99 %! [c,ia,ib] = intersect(a,b,'rows');
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100 %! assert(c,[1,1,2;1,4,5]);
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101 %! assert(ia,[1;2]);
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102 %! assert(ib,[3;1]);
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103 %! assert(a(ia,:),c);
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104 %! assert(b(ib,:),c);
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105 %!test
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106 %! a = [1 1 1 2 2 2];
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107 %! b = [1 2 3 4 5 6];
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108 %! c = intersect(a,b);
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109 %! assert(c, [1,2]);
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110 %!test
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111 %! a = [1 2 3 4; 5 6 7 8; 9 10 11 12];
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112 %! [b, ia, ib] = intersect(a, a, "rows");
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113 %! assert(b, a);
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114 %! assert(ia, [1:3]');
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115 %! assert(ib, [1:3]');
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