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% STK_MINDIST computes the separation distance of a set of points
%
% CALL: D = stk_mindist(X)
%
% computes the separation distance D of X. More precisely, if X is an
% n x d matrix, then
%
% D = min_{1 <= i < j <= n} norm(X(i,:) - X(j,:)),
%
% where norm(.) denotes the Euclidean norm in R^d.
%
% See also: stk_dist, stk_filldist
% Copyright Notice
%
% Copyright (C) 2018 CentraleSupelec
% Copyright (C) 2012, 2013 SUPELEC
%
% Authors: Julien Bect <julien.bect@centralesupelec.fr>
% Emmanuel Vazquez <emmanuel.vazquez@centralesupelec.fr>
% Copying Permission Statement
%
% This file is part of
%
% STK: a Small (Matlab/Octave) Toolbox for Kriging
% (https://github.com/stk-kriging/stk/)
%
% STK 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.
%
% STK 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 STK. If not, see <http://www.gnu.org/licenses/>.
function md = stk_mindist(x)
% call MEX-file
md = __stk_mindist_mex__(double(x));
end % function
%%
% Check that both double-precision matrices and stk_dataframe objects are accepted
%!test
%! d = 3; x = rand(7, d);
%! md1 = stk_mindist(x);
%! md2 = stk_mindist(stk_dataframe(x));
%! assert(stk_isequal_tolabs(md1, md2));
%%
% Check that sk_mindist(x) is empty when x has zero lines
%!test
%! for nc = [0 5 10],
%! x = zeros(0, nc);
%! d = stk_mindist(x);
%! assert(isempty(d));
%! end
%%
% Check that sk_mindist(x) is empty when x has only one line.
%!test
%! for nc = [0 5 10],
%! x = rand(1, nc);
%! d = stk_mindist(x);
%! assert(isempty(d));
%! end
%%
% Check that sk_mindist(x) is 0.0 when x has 0 columns (but at least 2 lines)
%!test
%! for nr = [2 5 10],
%! x = zeros(nr, 0);
%! d = stk_mindist(x);
%! assert(isequal(d, 0.0));
%! end
%%
% Random matrices with at least 2 lines and 1 column
%!test
%!
%! nrep = 20;
%! TOL_REL = 1e-15;
%!
%! for irep = 1:nrep,
%!
%! n = 2 + floor(rand * 10);
%! d = 1 + floor(rand * 10);
%! x = rand(n, d);
%! z = stk_mindist(x);
%!
%! assert(isequal(size(d), [1, 1]));
%! assert(~isnan(d));
%! assert(~isinf(d));
%!
%! % check the result
%! mindist = Inf;
%! for i = 1:(n-1),
%! for j = (i+1):n,
%! mindist = min(mindist, norm(x(i,:) - x(j,:)));
%! end
%! end
%! assert(abs(z - mindist) <= TOL_REL * mindist);
%!
%! end
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