ows specification of constant
  (fixed), nearest neighbor, certain locally adaptive variable bandwidths,
  and combinations of these. Also related to the smoothing parameter
  are the local polynmial degree and weight function.

    'nn' 'Nearest neighbor' smoothing parameter. Specifying 'nn',0.5
         means that the width of each smoothing neighborhood is chosen
         to cover 50% of the data.

     'h' A constant (or fixed) bandwidth parameter. For example, 'h',2
         means that the sm