Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / geometry-1.5.0 / graphs / knnGraph.m

diff --git a/octave_packages/geometry-1.5.0/graphs/knnGraph.m b/octave_packages/geometry-1.5.0/graphs/knnGraph.m
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+%% Copyright (C) 2008-2012 David Legland <david.legland@grignon.inra.fr>
+%% All rights reserved.
+%%
+%% Redistribution and use in source and binary forms, with or without
+%% modification, are permitted provided that the following conditions are met:
+%%
+%%   1 Redistributions of source code must retain the above copyright notice,
+%%   this list of conditions and the following disclaimer.
+%%   2 Redistributions in binary form must reproduce the above copyright
+%%   notice, this list of conditions and the following disclaimer in the
+%%   documentation and/or other materials provided with the distribution.
+%%
+%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
+%% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+%% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+%% ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
+%% ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+%% DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+%% SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+%% CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+%% OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+%% OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+%%
+%% 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
+
+%% -*- texinfo -*-
+%% @deftypefn {Function File} {@var{edges} = } knnGrpah (@var{nodes})
+%% Create the k-nearest neighbors graph of a set of points
+%%
+%% EDGES = knnGraph(NODES)
+%%
+%% Example
+%% @example
+%%
+%% nodes = rand(10, 2);
+%% edges = knnGraph(nodes);
+%% drawGraph(nodes, edges);
+%%
+%% @end example
+%%
+%% @end deftypefn
+
+function edges = knnGraph(nodes, varargin)
+
+  % get number of neighbors for each node
+  k = 2;
+  if ~isempty(varargin)
+  k = varargin{1};
+  end
+
+  % init size of arrays
+  n   = size(nodes, 1);
+  edges = zeros(k*n, 2);
+
+  % iterate on nodes
+  for i = 1:n
+  dists = distancePoints(nodes(i,:), nodes);
+  [dists inds]  = sort(dists); %#ok<ASGLU>
+  for j = 1:k
+    edges(k*(i-1)+j, :) = [i inds(j+1)];
+  end
+  end
+
+  % remove double edges
+  edges = unique(sort(edges, 2), 'rows');
+
+endfunction
+
+%!demo
+%! nodes = rand(10, 2);
+%! edges = knnGraph(nodes);
+%! drawGraph(nodes, edges);
+%! axis tight