qq {lattice}  R Documentation 
QuantileQuantile plots for comparing two Distributions
qq(x, ...) ## S3 method for class 'formula': qq(x, data = parent.frame(), aspect = "fill", panel = panel.qq, prepanel, scales, strip, groups, xlab, xlim, ylab, ylim, f.value = NULL, drop.unused.levels = lattice.getOption("drop.unused.levels"), ..., default.scales = list(), subscripts, subset)
x 
The object on which method dispatch is carried out.
For the formula method, a formula of the form y ~ x  g1 * g2
* ... , where x must be a numeric, and y can be a
factor, shingle, character or numeric vector, with the restriction
that there must be exactly two levels of y , which divide the
values of x into two groups. Quantiles for these groups will
be plotted along the two axes.

data 
For the formula methods, 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.

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.
f.value defaults to NULL , which is equivalent to
using 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 qqplot but
different from the default qq behaviour in SPLUS.
For large data, this argument can be useful in plotting a smaller set of quantiles, which is usually enough to capture the pattern. 
panel 
The function that uses the packet (subset of display variables) corresponding to a panel to create a display. Default panel functions are documented separately, and often have arguments that can be used to customize its display in various ways. Such arguments can usually be directly supplied to the high level function. 
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.

qq
produces a QQ plot of two samples. The default behaviour
of qq
is different from the corresponding SPLUS function. See
the entry for 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 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.qq
,
qqmath
, Lattice
qq(voice.part ~ height, aspect = 1, data = singer, subset = (voice.part == "Bass 2"  voice.part == "Tenor 1"))