| % File src/library/stats/man/update.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2011 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{update} |
| \title{Update and Re-fit a Model Call} |
| \alias{update} |
| \alias{update.default} |
| \alias{getCall} |
| \alias{getCall.default} |
| \usage{ |
| update(object, \dots) |
| \method{update}{default}(object, formula., \dots, evaluate = TRUE) |
| |
| getCall(x, \dots) |
| } |
| \arguments{ |
| \item{object, x}{An existing fit from a model function such as \code{lm}, |
| \code{glm} and many others.} |
| \item{formula.}{Changes to the formula -- see \code{update.formula} for |
| details.} |
| \item{\dots}{Additional arguments to the call, or arguments with |
| changed values. Use \code{name = NULL} to remove the argument \code{name}.} |
| \item{evaluate}{If true evaluate the new call else return the call.} |
| } |
| \description{ |
| \code{update} will update and (by default) re-fit a model. It does this |
| by extracting the call stored in the object, updating the call and (by |
| default) evaluating that call. Sometimes it is useful to call |
| \code{update} with only one argument, for example if the data frame has |
| been corrected. |
| |
| \dQuote{Extracting the call} in \code{update()} and similar functions |
| uses \code{getCall()} which itself is a (S3) generic function with a |
| default method that simply gets \code{x$call}. |
| |
| Because of this, \code{update()} will often work (via its default |
| method) on new model classes, either automatically, or by providing a |
| simple \code{getCall()} method for that class. |
| } |
| \value{ |
| If \code{evaluate = TRUE} the fitted object, otherwise the updated call. |
| } |
| \seealso{ |
| \code{\link{update.formula}} |
| } |
| \references{ |
| Chambers, J. M. (1992) |
| \emph{Linear models.} |
| Chapter 4 of \emph{Statistical Models in S} |
| eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole. |
| } |
| \examples{ |
| oldcon <- options(contrasts = c("contr.treatment", "contr.poly")) |
| ## Annette Dobson (1990) "An Introduction to Generalized Linear Models". |
| ## Page 9: Plant Weight Data. |
| ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14) |
| trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69) |
| group <- gl(2, 10, 20, labels = c("Ctl", "Trt")) |
| weight <- c(ctl, trt) |
| lm.D9 <- lm(weight ~ group) |
| lm.D9 |
| summary(lm.D90 <- update(lm.D9, . ~ . - 1)) |
| options(contrasts = c("contr.helmert", "contr.poly")) |
| update(lm.D9) |
| getCall(lm.D90) # "through the origin" |
| |
| options(oldcon) |
| } |
| \keyword{models} |