

   EExxttrraacctt ccoommppoonneennttss ffrroomm aa mmooddeell ffrraammee

        model.extract(frame, component)
        model.offset(frame)
        model.response(frame)

   AArrgguummeennttss::

      frame: A model frame

   component: The name of a components to extract, such as
             `"weights"', `"subset"'

   DDeessccrriippttiioonn::

        Returns the response, offset, subset, weights or other
        special components of a model frame passed as optional
        arguments to `model.frame'. `model.offset' and
        `model.response' are equivalent to `model.frame(,"off-
        set")' and `model.frame(,"response")' respectively.

   VVaalluuee::

        The specified component of the model frame, usually a
        vector.

   SSeeee AAllssoo::

        `model.frame', `offset'

   EExxaammpplleess::

        data(esoph)
        a <- model.frame(cbind(ncases,ncontrols) ~ agegp+tobgp+alcgp,data=esoph)
        model.extract(a,"response")
        all(model.extract(a,"response") == model.response(a))

        a <- model.frame(ncases/(ncases+ncontrols) ~ agegp+tobgp+alcgp,
                         data = esoph, weights = ncases+ncontrols)
        model.response(a)
        model.extract(a,"weights")

        a <- model.frame(cbind(ncases,ncontrols) ~ agegp,
                         something = tobgp, data = esoph)
        names(a)
        all(model.extract(a,"something")==esoph$tobgp) # TRUE

