| % File src/library/stats/man/expand.model.frame.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{expand.model.frame} |
| \alias{expand.model.frame} |
| \title{Add new variables to a model frame} |
| \description{ |
| Evaluates new variables as if they had been part of the formula of the |
| specified model. This ensures that the same \code{na.action} and |
| \code{subset} arguments are applied and allows, for example, \code{x} |
| to be recovered for a model using \code{sin(x)} as a predictor. |
| } |
| \usage{ |
| expand.model.frame(model, extras, |
| envir = environment(formula(model)), |
| na.expand = FALSE) |
| } |
| \arguments{ |
| \item{model}{a fitted model} |
| \item{extras}{one-sided formula or vector of character strings |
| describing new variables to be added} |
| \item{envir}{an environment to evaluate things in} |
| \item{na.expand}{logical; see below} |
| } |
| \details{ |
| If \code{na.expand = FALSE} then \code{NA} values in the extra variables |
| will be passed to the \code{na.action} function used in |
| \code{model}. This may result in a shorter data frame (with |
| \code{\link{na.omit}}) or an error (with \code{\link{na.fail}}). If |
| \code{na.expand = TRUE} the returned data frame will have precisely the |
| same rows as \code{model.frame(model)}, but the columns corresponding to |
| the extra variables may contain \code{NA}. |
| } |
| \value{ |
| A data frame. |
| } |
| \seealso{\code{\link{model.frame}}, \code{\link{predict}}} |
| |
| \examples{ |
| model <- lm(log(Volume) ~ log(Girth) + log(Height), data = trees) |
| expand.model.frame(model, ~ Girth) # prints data.frame like |
| |
| dd <- data.frame(x = 1:5, y = rnorm(5), z = c(1,2,NA,4,5)) |
| model <- glm(y ~ x, data = dd, subset = 1:4, na.action = na.omit) |
| expand.model.frame(model, "z", na.expand = FALSE) # = default |
| expand.model.frame(model, "z", na.expand = TRUE) |
| } |
| \keyword{manip} |
| \keyword{regression} |