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1 ## Copyright (C) 2000 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 2, or (at your option) |
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8 ## 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, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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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 ## |
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28 ## Return index vectors @var{ia} and @var{ib} such that @code{a(ia)==c} and |
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29 ## @code{b(ib)==c}. |
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30 ## |
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31 ## @end deftypefn |
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32 ## @seealso{unique, union, setxor, setdiff, ismember} |
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33 |
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34 function [c, ia, ib] = intersect (a, b) |
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35 if (nargin != 2) |
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36 usage ("intersect (a, b)"); |
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37 endif |
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38 |
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39 if (isempty (a) || isempty (b)) |
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40 c = ia = ib = []; |
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41 else |
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42 ## form a and b into sets |
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43 [a, ja] = unique (a); |
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44 [b, jb] = unique (b); |
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45 |
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46 c = [a(:); b(:)]; |
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47 [c, ic] = sort (c); ## [a(:);b(:)](ic) == c |
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48 |
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49 ii = find( c(1:end-1) == c(2:end) ); |
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50 |
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51 c = c(ii); ## The answer |
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52 ia = ja(ic(ii)); ## a(ia) == c |
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53 ib = jb(ic(ii+1) - length (a)); ## b(ib) == c |
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54 |
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55 |
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56 if (size (b, 1) == 1 || size (a, 1) == 1) |
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57 c = c.'; |
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58 endif |
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59 endif |
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60 |
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61 endfunction |
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62 |
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63 |
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64 %!# Test the routine for index vectors ia and ib |
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65 %!test |
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66 %! a = [3 2 4 5 7 6 5 1 0 13 13]; |
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67 %! b = [3 5 12 1 1 7]; |
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68 %! [c,ia,ib] = intersect(a,b); |
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69 %! assert( c,[1 3 5 7]); |
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70 %! assert(ia,[8 1 7 5]); |
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71 %! assert(ib,[5 1 2 6]); |
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72 %! assert(a(ia),c); |
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73 %! assert(b(ib),c); |
