$$ z=\frac{\sum{i=1}^{n} z_i* \frac{1}{d_i}} {\sum{i=1}^{n}\frac{1}{d_i}}
$$
$$ w_i=\frac{1}{d_i}
$$ z(x)=\frac{\sum{i=1}^{n} z_i* w_i} {\sum{i=1}^{n}*w_i}
