lppm(X, ...)"lpp" specifying a point pattern
    on a linear network.ppm."lppm" representing the fitted model.
  There are methods for print, predict,
  coef and similar functions.ppm designed
  to work with objects of class "lpp" instead of "ppp".  The argument X should be an object of class "lpp"
  (created by the command lpp) specifying a point pattern
  on a linear network.
  The subsequent arguments ... will be passed to
  ppm. They specify the form of the model.
McSwiggan, G., Nair, M.G. and Baddeley, A. (2012) Fitting Poisson point process models to events on a linear network. Manuscript in preparation.
methods.lppm,
  predict.lppm,
  ppm,
  lpp.