residuals.locfit is implemented as a front-end to
  fitted.locfit, with the type argument set.## S3 method for class 'locfit':
residuals(object, data, type="dev",
                  ...)"locfit" object."fit" for
  fitted.locfit, and "dev" for residuals.locfit.
  Other choices include "pear" forfitted.locfit; e.g.,
           cv and studentize.