| % File src/library/stats/man/dummy.coef.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2013 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{dummy.coef} |
| \title{Extract Coefficients in Original Coding} |
| \usage{ |
| dummy.coef(object, \dots) |
| |
| \method{dummy.coef}{lm}(object, use.na = FALSE, \dots) |
| |
| \method{dummy.coef}{aovlist}(object, use.na = FALSE, \dots) |
| } |
| \alias{dummy.coef} |
| \alias{dummy.coef.lm} |
| \alias{dummy.coef.aovlist} |
| \arguments{ |
| \item{object}{a linear model fit.} |
| \item{use.na}{logical flag for coefficients in a singular model. If |
| \code{use.na} is true, undetermined coefficients will be missing; if |
| false they will get one possible value.} |
| \item{\dots}{arguments passed to or from other methods.} |
| } |
| \description{ |
| This extracts coefficients in terms of the original levels of the |
| coefficients rather than the coded variables. |
| } |
| \details{ |
| A fitted linear model has coefficients for the contrasts of the factor |
| terms, usually one less in number than the number of levels. This |
| function re-expresses the coefficients in the original coding; as the |
| coefficients will have been fitted in the reduced basis, any implied |
| constraints (e.g., zero sum for \code{contr.helmert} or \code{contr.sum}) |
| will be respected. There will be little point in using |
| \code{dummy.coef} for \code{contr.treatment} contrasts, as the missing |
| coefficients are by definition zero. |
| |
| The method used has some limitations, and will give incomplete results |
| for terms such as \code{poly(x, 2)}. However, it is adequate for |
| its main purpose, \code{aov} models. |
| } |
| \value{ |
| A list giving for each term the values of the coefficients. For a |
| multistratum \code{aov} model, such a list for each stratum. |
| } |
| |
| \section{Warning}{ |
| This function is intended for human inspection of the |
| output: it should not be used for calculations. Use coded variables |
| for all calculations. |
| |
| The results differ from S for singular values, where S can be incorrect. |
| } |
| |
| \seealso{\code{\link{aov}}, \code{\link{model.tables}}} |
| |
| \examples{ |
| options(contrasts = c("contr.helmert", "contr.poly")) |
| ## From Venables and Ripley (2002) p.165. |
| npk.aov <- aov(yield ~ block + N*P*K, npk) |
| dummy.coef(npk.aov) |
| |
| npk.aovE <- aov(yield ~ N*P*K + Error(block), npk) |
| dummy.coef(npk.aovE) |
| } |
| \keyword{models} |