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## Copyright (C) 2024 David Legland
## 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.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function varargout = cvtUpdate(germs, points)
%CVTUPDATE Update germs of a CVT with given points.
%
% G2 = cvtUpdate(G, PTS)
% G: inital germs
% PTS: the points
%
% Example
% G = randPointDiscUnif(50);
% P = randPointDiscUnif(10000);
% G2 = cvtUpdate(G, P);
%
% See also
%
%
% Rewritten from programs found in
% http://people.scs.fsu.edu/~burkardt/m_src/cvt/cvt.html
%
% Reference:
% Qiang Du, Vance Faber, and Max Gunzburger,
% Centroidal Voronoi Tessellations: Applications and Algorithms,
% SIAM Review, Volume 41, 1999, pages 637-676.
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2007-10-10, using Matlab 7.4.0.287 (R2007a)
% Copyright 2007-2023 INRA - BIA PV Nantes - MIAJ Jouy-en-Josas
%% Init
% number of germs and of points
Ng = size(germs, 1);
N = size(points, 1);
% initialize centroids with values of germs
centroids = germs;
% number of updates of each centroid
count = ones(Ng, 1);
%% Generate random points
% for each point, determines which germ is the closest ones
[dist, ind] = minDistancePoints(points, germs); %#ok<ASGLU>
h = zeros(Ng, 1);
for i = 1:Ng
h(i) = sum(ind==i);
end
%% Centroids update
% add coordinate of each point to closest centroid
energy = 0;
for j = 1:N
centroids(ind(j), :) = centroids(ind(j), :) + points(j, :);
energy = energy + sum ( ( centroids(ind(j), :) - points(j, :) ).^2);
count(ind(j)) = count(ind(j)) + 1;
end
% estimate coordinate by dividing by number of counts
centroids = centroids ./ repmat(count, 1, size(germs, 2));
% normalizes energy by number of sample points
energy = energy / N;
%% Format output
varargout{1} = centroids;
if nargout > 1
varargout{2} = energy;
end
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