| % File src/library/stats/man/terms.formula.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2012 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{terms.formula} |
| \alias{terms.formula} |
| \title{Construct a terms Object from a Formula} |
| \description{ |
| This function takes a formula and some optional arguments and |
| constructs a terms object. The terms object can then be used to |
| construct a \code{\link{model.matrix}}. |
| } |
| \usage{ |
| \method{terms}{formula}(x, specials = NULL, abb = NULL, data = NULL, neg.out = TRUE, |
| keep.order = FALSE, simplify = FALSE, \dots, |
| allowDotAsName = FALSE) |
| } |
| \arguments{ |
| \item{x}{a formula.} |
| \item{specials}{which functions in the formula should be marked as |
| special in the \code{terms} object? A character vector or \code{NULL}.} |
| \item{abb}{Not implemented in \R.} |
| \item{data}{a data frame from which the meaning of the special symbol |
| \code{.} can be inferred. It is unused if there is no \code{.} in |
| the formula.} |
| \item{neg.out}{Not implemented in \R.} |
| \item{keep.order}{a logical value indicating whether the terms should |
| keep their positions. If \code{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.} |
| \item{simplify}{should the formula be expanded and simplified, the |
| pre-1.7.0 behaviour?} |
| \item{\dots}{further arguments passed to or from other methods.} |
| \item{allowDotAsName}{normally \code{.} in a formula refers to the |
| remaining variables contained in \code{data}. Exceptionally, |
| \code{.} can be treated as a name for non-standard uses of formulae.} |
| } |
| \details{ |
| Not all of the options work in the same way that they do in S and not |
| all are implemented. |
| } |
| \value{ |
| A \code{\link{terms.object}} object is returned. The object itself is |
| the re-ordered (unless \code{keep.order = TRUE}) formula. In all |
| cases variables within an interaction term in the formula are |
| re-ordered by the ordering of the \code{"variables"} attribute, which |
| is the order in which the variables occur in the formula. |
| } |
| \seealso{ |
| \code{\link{terms}}, \code{\link{terms.object}} |
| } |
| \keyword{models} |