

   MMooddiiffyy tteerrmmss oobbjjeeccttss

        delete.response(termobj)
        reformulate(termlabels,response=NULL)
        drop.terms(termobj, dropx = NULL, keep.response = FALSE)

   AArrgguummeennttss::

    termobj: A `terms' object

   termlabels: vector of strings giving the right-hand side of
             a model formula

   response: string giving the left-hand side of a model for-
             mula

      dropx: vector of positions of variables to drop from the
             right-hand side of the model

   keep.response: Keep the response in the resulting object?

   DDeessccrriippttiioonn::

        `delete.response' returns a `terms' object for the same
        model but with no response variable. `drop.terms'
        removes variables from the right-hand side of the
        model. `reformulate' creates a formula from a vector of
        strings.

   VVaalluuee::

        `delete.response' and `drop.terms' return a `terms'
        object; `reformulate' returns a `formula'.

   SSeeee AAllssoo::

        `terms'

   EExxaammpplleess::

        ff<-y~z+x+w
        tt<-terms(ff)
        tt
        delete.response(tt)
        drop.terms(tt,2:3,keep.response=T)
        reformulate(attr(tt,"term.labels"))

