https://github.com/cran/lattice
Tip revision: 01ca7cfc46c13ce55a9ded37d1feafd0edde1a42 authored by Deepayan Sarkar on 08 January 2013, 00:00:00 UTC
version 0.20-13
version 0.20-13
Tip revision: 01ca7cf
qqmath.Rd
\name{B_04_qqmath}
\alias{qqmath}
\alias{qqmath.formula}
\alias{qqmath.numeric}
\title{Q-Q Plot with Theoretical Distribution}
\description{
Draw quantile-Quantile plots of a sample against a theoretical
distribution, possibly conditioned on other variables.
}
\usage{
qqmath(x, data, \dots)
\method{qqmath}{formula}(x,
data,
allow.multiple = is.null(groups) || outer,
outer = !is.null(groups),
distribution = qnorm,
f.value = NULL,
auto.key = FALSE,
aspect = "fill",
panel = lattice.getOption("panel.qqmath"),
prepanel = NULL,
scales, strip, groups,
xlab, xlim, ylab, ylim,
drop.unused.levels = lattice.getOption("drop.unused.levels"),
\dots,
lattice.options = NULL,
default.scales = list(),
default.prepanel = lattice.getOption("prepanel.default.qqmath"),
subscripts,
subset)
\method{qqmath}{numeric}(x, data = NULL, ylab, \dots)
}
\arguments{
\item{x}{
The object on which method dispatch is carried out.
For the \code{"formula"} method, \code{x} should be a formula of the
form \code{~ x | g1 * g2 * \dots}, where \code{x} should be a
numeric variable. For the \code{"numeric"} method, \code{x} should
be a numeric vector.
}
\item{data}{
For the \code{formula} method, an optional data source (usually a
data frame) in which variables are to be evaluated (see
\code{\link{xyplot}} for details). \code{data} should not be
specified for the other methods, and is ignored with a warning if it
is.
}
\item{distribution}{
A quantile function that takes a vector of probabilities as argument
and produces the corresponding quantiles from a theoretical
distribution. Possible values are \code{\link{qnorm}},
\code{\link{qunif}}, etc. Distributions with other required
arguments need to be provided as user-defined functions (see example
with \code{\link{qt}}).
}
\item{f.value}{
An optional numeric vector of probabilities, quantiles corresponding
to which should be plotted. This can also be a function of a single
integer (representing sample size) that returns such a numeric
vector. A typical value for this argument is the function
\code{ppoints}, which is also the S-PLUS default. If specified, the
probabilities generated by this function is used for the plotted
quantiles, through the \code{\link{quantile}} function for the
sample, and the function specified as the \code{distribution}
argument for the theoretical distribution.
\code{f.value} defaults to \code{NULL}, which has the effect of
using \code{ppoints} for the quantiles of the theoretical
distribution, but the exact data values for the sample. This is
similar to what happens for \code{qqnorm}, but different from the
S-PLUS default of \code{f.value=ppoints}.
For large \code{x}, this argument can be used to restrict the number
of points plotted. See also the \code{tails.n} argument in
\code{\link{panel.qqmath}}.
}
\item{panel}{
A function, called once for each panel, that uses the packet (subset
of panel variables) corresponding to the panel to create a display.
The default panel function \code{\link{panel.qqmath}} is documented
separately, and has arguments that can be used to customize its
output in various ways. Such arguments can usually be directly
supplied to the high-level function.
}
\item{allow.multiple, outer}{ See \code{\link{xyplot}}. }
\item{auto.key}{ See \code{\link{xyplot}}. }
\item{aspect}{ See \code{\link{xyplot}}. }
\item{prepanel}{ See \code{\link{xyplot}}. }
\item{scales}{ See \code{\link{xyplot}}. }
\item{strip}{ See \code{\link{xyplot}}. }
\item{groups}{ See \code{\link{xyplot}}. }
\item{xlab, ylab}{ See \code{\link{xyplot}}. }
\item{xlim, ylim}{ See \code{\link{xyplot}}. }
\item{drop.unused.levels}{ See \code{\link{xyplot}}. }
\item{lattice.options}{ See \code{\link{xyplot}}. }
\item{default.scales}{ See \code{\link{xyplot}}. }
\item{subscripts}{ See \code{\link{xyplot}}. }
\item{subset}{ See \code{\link{xyplot}}. }
\item{default.prepanel}{
Fallback prepanel function. See \code{\link{xyplot}}.
}
\item{\dots}{
Further arguments. See corresponding entry in \code{\link{xyplot}}
for non-trivial details.
}
}
\value{
An object of class \code{"trellis"}. The
\code{\link[lattice:update.trellis]{update}} method can be used to
update components of the object and the
\code{\link[lattice:print.trellis]{print}} method (usually called by
default) will plot it on an appropriate plotting device.
}
\details{
\code{qqmath} produces Q-Q plots of the given sample against a
theoretical distribution. The default behaviour of \code{qqmath} is
different from the corresponding S-PLUS function, but is similar to
\code{qqnorm}. See the entry for \code{f.value} for specifics.
The implementation details are also different from S-PLUS. In
particular, all the important calculations are done by the panel (and
prepanel function) and not \code{qqmath} itself. In fact, both the
arguments \code{distribution} and \code{f.value} are passed unchanged
to the panel and prepanel function. This allows, among other things,
display of grouped Q-Q plots, which are often useful. See the help
page for \code{\link{panel.qqmath}} for further details.
This and all other high level Trellis functions have several arguments
in common. These are extensively documented only in the help page for
\code{\link{xyplot}}, which should be consulted to learn more detailed
usage.
}
\author{Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}}
\seealso{\code{\link{xyplot}}, \code{\link{panel.qqmath}},
\code{\link{panel.qqmathline}}, \code{\link{prepanel.qqmathline}},
\code{\link{Lattice}}, \code{\link{quantile}}
}
\examples{
qqmath(~ rnorm(100), distribution = function(p) qt(p, df = 10))
qqmath(~ height | voice.part, aspect = "xy", data = singer,
prepanel = prepanel.qqmathline,
panel = function(x, ...) {
panel.qqmathline(x, ...)
panel.qqmath(x, ...)
})
vp.comb <-
factor(sapply(strsplit(as.character(singer$voice.part), split = " "),
"[", 1),
levels = c("Bass", "Tenor", "Alto", "Soprano"))
vp.group <-
factor(sapply(strsplit(as.character(singer$voice.part), split = " "),
"[", 2))
qqmath(~ height | vp.comb, data = singer,
groups = vp.group, auto.key = list(space = "right"),
aspect = "xy",
prepanel = prepanel.qqmathline,
panel = function(x, ...) {
panel.qqmathline(x, ...)
panel.qqmath(x, ...)
})
}
\keyword{dplot}