R: Quantile-Quantile Plots of Two Samples

B_05_qq {lattice}

R Documentation

Quantile-Quantile Plots of Two Samples

Description

Quantile-Quantile plots for comparing two Distributions

Usage

qq(x, data, ...)

## S3 method for class 'formula'
qq(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"),
   ...,
   lattice.options = NULL,
   qtype = 7,
   default.scales = list(),
   default.prepanel = lattice.getOption("prepanel.default.qq"),
   subscripts,
   subset)

## S3 method for class 'data.frame'
qq(x, data = NULL, formula = data, ...)

Arguments

`x`	The object on which method dispatch is carried out. For the `"formula"` method, `x` should be a formula of the form `y ~ x \| g1 * g2 * ...`, where `x` should be a numeric variable, and `y` a factor, shingle, character, or numeric variable, 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 against each other along the two axes.
`data`	For the `formula` method, an optional data source (usually a data frame) in which variables are to be evaluated (see `xyplot` for details).
`formula`	The formula to be used for the `"data.frame"` method. See documentation for argument `x` for details.
`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 `ppoints`, which is also the S-PLUS default. If specified, the probabilities generated by this function is used for the plotted quantiles, through the `quantile` function. `f.value` defaults to `NULL`, which is equivalent to 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 `qqplot` but different from the default behaviour of `qq` in S-PLUS. For large `x`, this argument can be used to restrict the number of quantiles plotted.
`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 `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.
`qtype`	The `type` argument for `quantile`.
`aspect`	See `xyplot`.
`prepanel`	See `xyplot`.
`scales`	See `xyplot`.
`strip`	See `xyplot`.
`groups`	See `xyplot`.
`xlab`, `ylab`	See `xyplot`.
`xlim`, `ylim`	See `xyplot`.
`drop.unused.levels`	See `xyplot`.
`lattice.options`	See `xyplot`.
`default.scales`	See `xyplot`.
`subscripts`	See `xyplot`.
`subset`	See `xyplot`.
`default.prepanel`	Fallback prepanel function. See `xyplot`.
`...`	Further arguments. See corresponding entry in `xyplot` for non-trivial details.

Details

qq produces Q-Q plots of two samples. The default behaviour of qq is different from the corresponding S-PLUS 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.

Value

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.

Author(s)

Deepayan Sarkar Deepayan.Sarkar@R-project.org

Examples

qq(voice.part ~ height, aspect = 1, data = singer,
   subset = (voice.part == "Bass 2" | voice.part == "Tenor 1"))

[Package lattice version 0.22-6 Index]