The R Project SVN R

\name{terms.object}
\title{Description of Terms Objects}
\description{
  An object of class \code{\link{terms}} holds information about a model.
  Usually the model was specified in terms of a \code{\link{formula}}
  and that formula was used to determine the terms object. 

  The object itself is simply the formula supplied to the call of
  \code{\link{terms.formula}}. The object has a number of attributes
  and they are used to construct the model frame.
}
\value{
  An object with the following attributes:
  \item{factors}{A matrix of variables by terms showing which variables
    appear in which terms.}
  \item{term.labels}{A character vector containing the labels for each
    of the terms in the model.}
  \item{variables}{A list of the variables in the model}
  \item{intercept}{Either 0, indicating no intercept is to be fit, or 1
    indicating that an intercept is to be fit.}
  \item{order}{A vector of the same length as \code{term.labels}
      indicating the order of interaction for each term }
  \item{response} {The index of the variable (in variables) of the
      response (the left hand side of the formula).}
  \item{offset}{If the model contains \code{\link{offset}} terms there
      is an \code{offset} attribute indicating which terms are offsets}
  \item{specials}{If the \code{specials} argument was given to
      \code{\link{terms.formula}} there is a \code{specials}
      attribute, a list of vectors indicating the terms that contain
      these special functions.} 
}
\note{
    These objects are different from those found in S. In particular there
    is no \code{formula} attribute, instead the object is itself a
    formula. Thus, the mode of a terms object is different as well.
}
\note{
    An example of the \code{specials} argument can be seen in the
    \code{\link{aov}} function.
}
  \seealso{
\code{\link{terms}}, \code{\link{terms.default}}, \code{\link{formula}}.
}
%%--- MM: I would really like instructive examples here...
\keyword{models}