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\name{B_05_qq}
\alias{qq}
\alias{qq.formula}
\title{ Quantile-Quantile Plots of Two Samples }
\description{
Quantile-Quantile plots for comparing two Distributions
}
\usage{
qq(x, data, \dots)
\method{qq}{formula}(x, data, aspect = "fill",
panel = lattice.getOption("panel.qq"),
prepanel, scales, strip,
groups, xlab, xlim, ylab, ylim, f.value = NULL,
drop.unused.levels = lattice.getOption("drop.unused.levels"),
\dots,
lattice.options = NULL,
qtype = 7,
default.scales = list(),
default.prepanel = lattice.getOption("prepanel.default.qq"),
subscripts,
subset)
}
\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{y ~ x | g1 * g2 * \dots}, where \code{x} should be a
numeric variable, and \code{y} a factor, shingle, character, or
numeric variable, with the restriction that there must be exactly
two levels of \code{y}, which divide the values of \code{x} into two
groups. Quantiles for these groups will be plotted against each
other along the two axes.
}
\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 other methods, and is ignored with a warning if it
% is.
}
\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{quantile} function.
\code{f.value} defaults to \code{NULL}, which is equivalent to
\preformatted{
f.value = function(n) ppoints(n, a = 1)
}
This has the effect of including the minimum and maximum data values
in the computed quantiles. This is similar to what happens for
\code{qqplot} but different from the default behaviour of \code{qq}
in S-PLUS.
For large \code{x}, this argument can be used to restrict the number
of quantiles plotted.
}
\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.qq}} 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{qtype}{ The \code{type} argument for \code{\link{quantile}}. }
\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.
}
\author{Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}}
\details{
\code{qq} produces Q-Q plots of two samples. The default behaviour of
\code{qq} is different from the corresponding S-PLUS function. See the
entry for \code{f.value} for specifics.
This and all other high level Trellis functions have several
arguments in common. These are extensively documented only in the
help page for \code{xyplot}, which should be consulted to learn more
detailed usage.
}
\seealso{\code{\link{xyplot}}, \code{\link{panel.qq}},
\code{\link{qqmath}}, \code{\link{Lattice}}
}
\examples{
qq(voice.part ~ height, aspect = 1, data = singer,
subset = (voice.part == "Bass 2" | voice.part == "Tenor 1"))
}
\keyword{dplot}
|
