function chisquared = chisquare( ha, hb )
%CHISQUARE generates a chisquare number from two histogram
    chisquared = double(0);
    for i=1:size(ha,1)
        if ha(i) ~= 0
            chisquared = double(chisquared) + power((hb(i) - ha(i)), 2)/ha(i);
        end
    end
end