if a data
argument is present in the calling sequence that
produced object
, the corresponding data frame (with
na.action
and subset
applied to it, if also present in
the call that produced object
) is returned;
else, NULL
is returned.
Note that as from version 3.1-102, this only omits rows omitted in the
fit if na.action = na.omit
, and does not omit at all if
na.action = na.exclude
. That is generally what is wanted for
plotting, the main use of this function.