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% File nlme/man/plot.lmList.Rd
% Part of the nlme package for R
% Distributed under GPL 2 or later: see nlme/LICENCE.note
\name{plot.lmList}
\title{Plot an lmList Object}
\usage{
\method{plot}{lmList}(x, form, abline, id, idLabels, grid, \dots)
}
\alias{plot.lmList}
\arguments{
\item{x}{an object inheriting from class \code{"\link{lmList}"}, representing
a list of \code{lm} objects with a common model.}
\item{form}{an optional formula specifying the desired type of
plot. Any variable present in the original data frame used to obtain
\code{x} can be referenced. In addition, \code{x} itself
can be referenced in the formula using the symbol
\code{"."}. Conditional expressions on the right of a \code{|}
operator can be used to define separate panels in a Trellis
display. Default is \code{resid(., type = "pool") ~ fitted(.) },
corresponding to a plot of the standardized residuals (using a pooled
estimate for the residual standard error) versus fitted values.
}
\item{abline}{an optional numeric value, or numeric vector of length
two. If given as a single value, a horizontal line will be added to the
plot at that coordinate; else, if given as a vector, its values are
used as the intercept and slope for a line added to the plot. If
missing, no lines are added to the plot.
}
\item{id}{an optional numeric value, or one-sided formula. If given as
a value, it is used as a significance level for a two-sided outlier
test for the standardized residuals. Observations with
absolute standardized residuals greater than the \eqn{1 - value/2}
quantile of the standard normal distribution are identified in the
plot using \code{idLabels}. If given as a one-sided formula, its
right hand side must evaluate to a logical, integer, or character
vector which is used to identify observations in the plot. If
missing, no observations are identified.
}
\item{idLabels}{an optional vector, or one-sided formula. If given as a
vector, it is converted to character and used to label the
observations identified according to \code{id}. If given as a
one-sided formula, its right hand side must evaluate to a vector
which is converted to character and used to label the identified
observations. Default is \code{getGroups(x)}.
}
\item{grid}{an optional logical value indicating whether a grid should
be added to plot. Default depends on the type of Trellis plot used:
if \code{xyplot} defaults to \code{TRUE}, else defaults to
\code{FALSE}.
}
\item{\dots}{optional arguments passed to the Trellis plot function.}
}
\description{
Diagnostic plots for the linear model fits corresponding to the
\code{x} components are obtained. The \code{form} argument gives
considerable flexibility in the type of plot specification. A
conditioning expression (on the right side of a \code{|} operator)
always implies that different panels are used for each level of the
conditioning factor, according to a Trellis display. If \code{form}
is a one-sided formula, histograms of the variable on the right hand
side of the formula, before a \code{|} operator, are displayed (the
Trellis function \code{histogram} is used). If \code{form} is
two-sided and both its left and right hand side variables are
numeric, scatter plots are displayed (the Trellis function
\code{xyplot} is used). Finally, if \code{form} is two-sided and its
left had side variable is a factor, box-plots of the right hand side
variable by the levels of the left hand side variable are displayed
(the Trellis function \code{bwplot} is used).
}
\value{
a diagnostic Trellis plot.
}
\author{José Pinheiro and Douglas Bates \email{bates@stat.wisc.edu}}
\seealso{\code{\link{lmList}},\code{\link{predict.lm}},
\code{\link[lattice]{xyplot}}, \code{\link[lattice]{bwplot}}, \code{\link[lattice]{histogram}}
}
\examples{
fm1 <- lmList(distance ~ age | Subject, Orthodont)
# standardized residuals versus fitted values by gender
plot(fm1, resid(., type = "pool") ~ fitted(.) | Sex, abline = 0, id = 0.05)
# box-plots of residuals by Subject
plot(fm1, Subject ~ resid(.))
# observed versus fitted values by Subject
plot(fm1, distance ~ fitted(.) | Subject, abline = c(0,1))
}
\keyword{models}
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