# qq: Quantile-Quantile Plots of Two Samples In lattice: Trellis Graphics for R

## Description

Quantile-Quantile plots for comparing two Distributions

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15``` ```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) ```

## 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). `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

`xyplot`, `panel.qq`, `qqmath`, `Lattice`

## Examples

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

### Example output ```
```

lattice documentation built on Sept. 22, 2021, 5:11 p.m.