the data.

 Required argument:
   fit  (produced by locfit()).

 Optional arguments:
   'nodata'  - don't add data to plot.
   'contour' - for 2-d predictors, use contour instead of surf.
   'direct'  - fit directly, instead of using interpolation
               (see the predict() function).
   'what'    - locfit what argument ('coef', 'infl', 'vari', 'band' etc).
   Any additional arguments are passed to Matlab's plot(), contour()
     or surf() function as appropriate.

 To add confidence ba