function unique_num = r8vec_unique_count ( n, a, tol )
%*****************************************************************************80
%
%% R8VEC_UNIQUE_COUNT counts the unique elements in an unsorted R8VEC.
%
% Discussion:
%
% Because the array is unsorted, this algorithm is O(N^2).
%
% If the tolerance is large enough, then the concept of uniqueness
% can become ambiguous. If we have a tolerance of 1.5, then in the
% list ( 1, 2, 3, 4, 5, 6, 7, 8, 9 ) is it fair to say we have only
% one unique entry? That would be because 1 may be regarded as unique,
% and then 2 is too close to 1 to be unique, and 3 is too close to 2 to
% be unique and so on.
%
% This seems wrongheaded. So I prefer the idea that an item is not
% unique under a tolerance only if it is close to something that IS unique.
% Thus, the unique items are guaranteed to cover the space if we include
% a disk of radius TOL around each one.
%
% Licensing:
%
% This code is distributed under the GNU LGPL license.
%
% Modified:
%
% 26 October 2008
%
% Author:
%
% John Burkardt
%
% Parameters:
%
% Input, integer N, the number of elements of A.
%
% Input, real A(N), the unsorted array to examine.
%
% Input, real TOL, a nonnegative tolerance for equality.
%
% Output, integer UNIQUE_NUM, the number of unique elements of A.
%
unique_num = 0;
for i1 = 1 : n
unique_num = unique_num + 1;
unique(i1) = 1;
for i2 = 1 : i1 - 1
if ( unique(i2) )
if ( abs ( a(i1) - a(i2) ) <= tol )
unique_num = unique_num - 1;
unique(i1) = 0;
break
end
end
end
end
return
end