Mercurial > octave-nkf
view scripts/set/ismember.m @ 7067:88417316c1b0
[project @ 2007-10-25 06:57:16 by jwe]
author | jwe |
---|---|
date | Thu, 25 Oct 2007 06:57:17 +0000 |
parents | a1dbe9d80eee |
children | 609fd2045523 |
line wrap: on
line source
## Copyright (C) 2000, 2005, 2006, 2007 Paul Kienzle ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} [@var{bool}, @var{index}] = ismember (@var{a}, @var{s}) ## Return a matrix @var{bool} the same shape as @var{a} which has 1 if ## @code{a(i,j)} is in @var{s} or 0 if it isn't. If a second output argument ## is requested, the indexes into @var{s} of the matching elements is ## also returned. ## @seealso{unique, union, intersection, setxor, setdiff} ## @end deftypefn ## Author: Paul Kienzle ## Adapted-by: jwe function [c, index] = ismember (a, s) if (nargin != 2) print_usage (); endif ## Convert char matrices to cell arrays. if (ischar (a)) a = cellstr (a); endif if (ischar (s)) s = cellstr (s); endif ## Input checking. if (! isa (a, class (s))) error ("ismember: both input arguments must be the same type"); endif if (iscell (a) && ! iscellstr (a)) error ("ismember: cell arrays may only contain strings"); endif if (! isnumeric(a) && ! iscell (a)) error ("ismember: input arguments must be arrays, cell arrays, or strings"); endif ## Do the actual work. if (isempty (a) || isempty (s)) c = zeros (size (a), "logical"); else if (numel (s) == 1) if (iscell (a)) c = strcmp (a, s); else ## Both A and S are matrices. c = (a == s); endif index = double (c); elseif (numel (a) == 1) if (iscell (a)) f = find (strcmp (a, s), 1); else ## Both A and S are matrices. f = find (a == s, 1); endif c = ! isempty (f); index = f; if (isempty (index)) index = 0; endif else ## Magic: the following code determines for each a, the index i ## such that S(i)<= a < S(i+1). It does this by sorting the a ## into S and remembering the source index where each element came ## from. Since all the a's originally came after all the S's, if ## the source index is less than the length of S, then the element ## came from S. We can then do a cumulative sum on the indices to ## figure out which element of S each a comes after. ## E.g., S=[2 4 6], a=[1 2 3 4 5 6 7] ## unsorted [S a] = [ 2 4 6 1 2 3 4 5 6 7 ] ## sorted [ S a ] = [ 1 2 2 3 4 4 5 6 6 7 ] ## source index p = [ 4 1 5 6 2 7 8 3 9 10 ] ## boolean p<=l(S) = [ 0 1 0 0 1 0 0 1 0 0 ] ## cumsum(p<=l(S)) = [ 0 1 1 1 2 2 2 3 3 3 ] ## Note that this leaves a(1) coming after S(0) which doesn't ## exist. So arbitrarily, we will dump all elements less than ## S(1) into the interval after S(1). We do this by dropping S(1) ## from the sort! E.g., S=[2 4 6], a=[1 2 3 4 5 6 7] ## unsorted [S(2:3) a] =[4 6 1 2 3 4 5 6 7 ] ## sorted [S(2:3) a] = [ 1 2 3 4 4 5 6 6 7 ] ## source index p = [ 3 4 5 1 6 7 2 8 9 ] ## boolean p<=l(S)-1 = [ 0 0 0 1 0 0 1 0 0 ] ## cumsum(p<=l(S)-1) = [ 0 0 0 1 1 1 2 2 2 ] ## Now we can use Octave's lvalue indexing to "invert" the sort, ## and assign all these indices back to the appropriate A and S, ## giving S_idx = [ -- 1 2], a_idx = [ 0 0 0 1 1 2 2 ]. Add 1 to ## a_idx, and we know which interval S(i) contains a. It is ## easy to now check membership by comparing S(a_idx) == a. This ## magic works because S starts out sorted, and because sort ## preserves the relative order of identical elements. lt = length (s); [s, sidx] = sort (s); [v, p] = sort ([s(2:lt); a(:)]); idx(p) = cumsum (p <= lt-1) + 1; idx = idx(lt:end); if (iscell (a) || iscell (s)) c = (cellfun ("length", a) == reshape (cellfun ("length", s(idx)), size (a))); idx2 = find (c); c(idx2) = all (char (a(idx2)) == char (s(idx)(idx2)), 2); index = zeros (size (c)); index(c) = sidx(idx(c)); else ## Both A and S are matrices. c = (a == reshape (s (idx), size (a))); index = zeros (size (c)); index(c) = sidx(idx(c)); endif endif endif endfunction %!assert (ismember ({''}, {'abc', 'def'}), false); %!assert (ismember ('abc', {'abc', 'def'}), true); %!assert (isempty (ismember ([], [1, 2])), true); %!xtest assert (ismember ('', {'abc', 'def'}), false); %!fail ('ismember ([], {1, 2})', 'error:.*'); %!fail ('ismember ({[]}, {1, 2})', 'error:.*'); %!assert (ismember ({'foo', 'bar'}, {'foobar'}), logical ([0, 0])) %!assert (ismember ({'foo'}, {'foobar'}), false) %!assert (ismember ({'bar'}, {'foobar'}), false) %!assert (ismember ({'bar'}, {'foobar', 'bar'}), true) %!assert (ismember ({'foo', 'bar'}, {'foobar', 'bar'}), logical ([0, 1])) %!assert (ismember ({'xfb', 'f', 'b'}, {'fb', 'b'}), logical ([0, 0, 1]))