function [z Z] = IDND6(I,O,q,Q)

% Yet another IDND alternative

N = size(I,1);
a = length(O);
if a ~= N
    error('I and O sizes do not match!')
end

if nargin < 3
    [q Q] = nc(O);
end

class{q} = []; NN(q) = 0;
for i = 1:q
    class{i} = find(O==Q(i));    
    NN(i) = length(class{i});
end

d(N,N) = Inf;
for i = 1:(N-1)
    X = ones((N-i),1)*I(i,:);
    d((i+1):N,i) = sum( (X - I((i+1):N,:)).^2,2 ) ;
    d(i,i) = Inf;
end

D = d + d'; % A compact form of the distance matrix
ZZ(N) = 0;

for i = 1:N
    f = find(O(i) == Q);
    ZZ(i) = (N / sum(1./(D(i,:)+eps)) - eps) / (NN(f) / sum(1./(D(i,class{f})+eps)) - eps);
end

Z = min(ZZ/2,1);
z = sum(Z>0.5)/N;