qqmath {lattice}  R Documentation 
QuantileQuantile plot of a sample and a theoretical distribution
qqmath(x, ...) ## S3 method for class 'formula': qqmath(x, data = parent.frame(), allow.multiple = is.null(groups)  outer, outer = !is.null(groups), distribution = qnorm, f.value = NULL, auto.key = FALSE, aspect = "fill", panel = "panel.qqmath", prepanel = NULL, scales, strip, groups, xlab, xlim, ylab, ylim, drop.unused.levels = lattice.getOption("drop.unused.levels"), ..., default.scales = list(), subscripts, subset) ## S3 method for class 'numeric': qqmath(x, data, ylab, ...)
x 
The object on which method dispatch is carried out.
For the "formula" method, a formula of the form ~ x 
g1 * g2 * ... , where x must be a numeric. For the
"numeric" method, a numeric vector.

data 
For the formula method, an optional data frame in which
variables in the formula (as well as groups and
subset , if any) are to be evaluated. By default, the
environment where the function was called from is used. Ignored
with a warning in other methods.

distribution 
a quantile function that takes a vector of
probabilities as argument and produces the corresponding
quantiles. Possible values are qnorm , qunif etc.
Distributions with other required arguments need to be passed in as
user defined functions.

f.value 
optional numeric vector of probabilities, quantiles
corresponding to which should be plotted. Can also be a function of
a single integer (representing sample size) that returns such a
numeric vector. The typical value for this argument is the function
ppoints , which is also the SPLUS default. If specified, the
probabilities generated by this function is used for the plotted
quantiles, using the quantile function for the sample, and
the function specified as the distribution argument for the
theoretical distribution.
f.value defaults to NULL , which has the effect of
using ppoints for the quantiles of the theoretical
distribution, but the exact data values for the sample. This is
similar to what happens for qqnorm , but different from the
SPLUS default of f.value=ppoints .
For large x , this argument can be useful in plotting a
smaller set of quantiles, which is usually enough to capture the
pattern.

panel 
The panel function to be used. Unlike in older versions, the
default panel function does most of the actual computations and has
support for grouping. See panel.qqmath for details.

allow.multiple, outer, auto.key, aspect, prepanel, scales,
strip, groups, xlab, xlim, ylab, ylim, drop.unused.levels,
default.scales, subscripts, subset 
See xyplot 
... 
Further arguments. See corresponding entry in xyplot
for nontrivial details.

qqmath
produces a QQ plot of the given sample and a
theoretical distribution. The default behaviour of qqmath
is
different from the corresponding SPLUS function, but is similar to
qqnorm
. See the entry for f.value
for specifics.
The implementation details are also different from SPLUS. In
particular, all the important calculations are done by the panel (and
prepanel function) and not qqmath
itself. In fact, both the
arguments distribution
and f.value
are passed unchanged
to the panel and prepanel function. This allows, among other things,
display of grouped QQ plots, which are often useful. See the help
page for 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 xyplot
, which should be consulted to learn more
detailed usage.
An object of class "trellis"
. The
update
method can be used to
update components of the object and the
print
method (usually called by
default) will plot it on an appropriate plotting device.
Deepayan Sarkar Deepayan.Sarkar@Rproject.org
xyplot
, panel.qqmath
,
panel.qqmathline
, prepanel.qqmathline
,
Lattice
, quantile
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, ...) })