| % File src/library/stats/man/alias.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2014 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{alias} |
| \title{Find Aliases (Dependencies) in a Model} |
| \usage{ |
| alias(object, \dots) |
| |
| \method{alias}{formula}(object, data, \dots) |
| |
| \method{alias}{lm}(object, complete = TRUE, partial = FALSE, |
| partial.pattern = FALSE, \dots) |
| } |
| \alias{alias} |
| \alias{alias.formula} |
| \alias{alias.lm} |
| \arguments{ |
| \item{object}{A fitted model object, for example from \code{lm} or |
| \code{aov}, or a formula for \code{alias.formula}.} |
| \item{data}{Optionally, a data frame to search for the objects |
| in the formula.} |
| \item{complete}{Should information on complete aliasing be included?} |
| \item{partial}{Should information on partial aliasing be included?} |
| \item{partial.pattern}{Should partial aliasing be presented in a |
| schematic way? If this is done, the results are presented in a |
| more compact way, usually giving the deciles of the coefficients.} |
| \item{\dots}{further arguments passed to or from other methods.} |
| } |
| \description{ |
| Find aliases (linearly dependent terms) in a linear model specified by |
| a formula. |
| } |
| \details{ |
| Although the main method is for class \code{"lm"}, \code{alias} is |
| most useful for experimental designs and so is used with fits from |
| \code{aov}. |
| Complete aliasing refers to effects in linear models that cannot be estimated |
| independently of the terms which occur earlier in the model and so |
| have their coefficients omitted from the fit. Partial aliasing refers |
| to effects that can be estimated less precisely because of |
| correlations induced by the design. |
| |
| Some parts of the \code{"lm"} method require recommended package |
| \CRANpkg{MASS} to be installed. |
| } |
| \value{ |
| A list (of \code{\link{class}} \code{"\link{listof}"}) containing components |
| \item{Model}{Description of the model; usually the formula.} |
| \item{Complete}{A matrix with columns corresponding to effects that |
| are linearly dependent on the rows.} |
| \item{Partial}{The correlations of the estimable effects, with a zero |
| diagonal. An object of class \code{"mtable"} which has its own |
| \code{\link{print}} method.} |
| } |
| \note{ |
| The aliasing pattern may depend on the contrasts in use: Helmert |
| contrasts are probably most useful. |
| |
| The defaults are different from those in S. |
| } |
| \references{ |
| Chambers, J. M., Freeny, A and Heiberger, R. M. (1992) |
| \emph{Analysis of variance; designed experiments.} |
| Chapter 5 of \emph{Statistical Models in S} |
| eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole. |
| } |
| \author{ |
| The design was inspired by the S function of the same name described |
| in Chambers \emph{et al} (1992). |
| } |
| \examples{\donttest{% as it loads MASS |
| op <- options(contrasts = c("contr.helmert", "contr.poly")) |
| npk.aov <- aov(yield ~ block + N*P*K, npk) |
| alias(npk.aov) |
| options(op) # reset |
| }} |
| \keyword{models} |