| terms.formula {stats} | R Documentation |
This function takes a formula and some optional arguments and
constructs a terms object. The terms object can then be used to
construct a model.matrix.
## S3 method for class 'formula':
terms(x, specials = NULL, abb = NULL, data = NULL, neg.out = TRUE,
keep.order = FALSE, simplify = FALSE, ...,
allowDotAsName = FALSE)
x |
a formula. |
specials |
which functions in the formula should be marked as
special in the terms object. |
abb |
Not implemented in R. |
data |
a data frame from which the meaning of the special symbol
. can be inferred. It is unused if there is no . in
the formula. |
neg.out |
Not implemented in R. |
keep.order |
a logical value indicating whether the terms should
keep their positions. If FALSE the terms are reordered so
that main effects come first, followed by the interactions,
all second-order, all third-order and so on. Effects of a given
order are kept in the order specified. |
simplify |
should the formula be expanded and simplified, the pre-1.7.0 behaviour? |
... |
further arguments passed to or from other methods. |
allowDotAsName |
normally . in a formula refers to the
remaining variables contained in data. Exceptionally,
. can be treated as a name for non-standard uses of formulae. |
Not all of the options work in the same way that they do in S and not all are implemented.
A terms.object object is returned. The object itself is
the re-ordered (unless keep.order = TRUE) formula. In all
cases variables within an interaction term in the formula are
re-ordered by the ordering of the "variables" attribute, which
is the order in which the variables occur in the formula.