Diagnostic plots for the linear model fits corresponding to the
object
components are obtained. The
form argument gives
considerable flexibility in the type of plot specification. A
conditioning expression (on the right side of a `|' operator)
always implies that different panels are used for each level of the
conditioning factor, according to a Trellis display. If
form
is a one-sided formula, histograms of the variable on the right hand
side of the formula, before a `|' operator, are displayed (the
Trellis function
histogram is used). If
form is
two-sided and both its left and right hand side variables are
numeric, scatter plots are displayed (the Trellis function
xyplot
is used). Finally, if
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
bwplot is used).
an object inheriting from class
lmList, representing
a list of
lm objects with a common model.
OPTIONAL ARGUMENTS:
form
an optional formula specifying the desired type of
plot. Any variable present in the original data frame used to obtain
object can be referenced. In addition,
object itself
can be referenced in the formula using the symbol
".". Conditional expressions on the right of a |
operator can be used to define separate panels in a Trellis
display. Default is `resid(., type = "pool") ~ fitted(.)',
corresponding to a plot of the standardized residuals (using a pooled
estimate for the residual standard error) versus fitted values.
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.
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 1 - value/2
quantile of the standard normal distribution are identified in the
plot using
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.
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
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
getGroups(object).
grid
an optional logical value indicating whether a grid should
be added to plot. Default depends on the type of Trellis plot used:
if
xyplot defaults to
TRUE, else defaults to
FALSE.
subset
an optional expression indicating the subset of the
observations that should be used in the plot. This can be a logical
vector, or a numeric vector indicating which observation numbers
are to be included, or a character vector of the row names to be
included. All observations are included by default.
...
optional arguments passed to the Trellis plot function.
VALUE:
a diagnostic Trellis plot.
SEE ALSO:
,
,
,
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))