tmd {lattice} | R Documentation

## Tukey Mean-Difference Plot

### Description

`tmd` Creates Tukey Mean-Difference Plots from a trellis object returned by `xyplot`, `qq` or `qqmath`. The prepanel and panel functions are used as appropriate. The `formula` method for `tmd` is provided for convenience, and simply calls `tmd` on the object created by calling `xyplot` on that formula.

### Usage

    tmd(object, ...)

    ## S3 method for class 'trellis':
    tmd(object,
        xlab = "mean",
        ylab = "difference",
        panel,
        prepanel,
        ...)

    prepanel.tmd.qqmath(x,
                 f.value = NULL,
                 distribution = qnorm,
                 qtype = 7,
                 groups = NULL,
                 subscripts, ...)
    panel.tmd.qqmath(x,
                 f.value = NULL,
                 distribution = qnorm,
                 qtype = 7,
                 groups = NULL,
                 subscripts, ...)
    panel.tmd.default(x, y, groups = NULL, ...)
    prepanel.tmd.default(x, y, ...)

### Arguments

`object` | An object of class `"trellis"` returned by `xyplot`, `qq` or `qqmath`.
`xlab` | x label
`ylab` | y label
`panel` | panel function to be used. See details below.
`prepanel` | prepanel function. See details below.
`f.value, distribution, qtype` | see `panel.qqmath`.
`groups, subscripts` | see `xyplot`.
`x, y` | data as passed to panel functions in original call.
`...` | other arguments

### Details

The Tukey Mean-difference plot is produced by modifying the (x,y) values of each panel as follows: the new coordinates are given by `x=(x+y)/2` and `y=y-x`, which are then plotted. The default panel function(s) add a reference line at `y=0` as well.

`tmd` acts on the a `"trellis"` object, not on the actual plot this object would have produced. As such, it only uses the arguments supplied to the panel function in the original call, and completely ignores what the original panel function might have done with this data. `tmd` uses these panel arguments to set up its own scales (using its `prepanel` argument) and display (using `panel`). It is thus important to provide suitable prepanel and panel functions to `tmd` depending on the original call.

Such functions currently exist for `xyplot`, `qq` (the ones with `default` in their name) and `qqmath`, as listed in the usage section above. These assume the default displays for the corresponding high-level call. If unspecified, the code{prepanel} and `panel` arguments default to suitable choices.

`tmd` uses the `update` method for `"trellis"` objects, which processes all extra arguments supplied to `tmd`.

### 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

### See Also

`qq`, `qqmath`, `xyplot`, `Lattice`

### Examples

    tmd(qqmath(~height | voice.part, data = singer))

[Package lattice version 0.16-5 Index]