tmd {lattice}R Documentation

Tukey Mean-Difference Plot


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.


tmd(object, ...)

## S3 method for class 'trellis':
    xlab = "mean",
    ylab = "difference",

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


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


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.


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

See Also

qq, qqmath, xyplot, Lattice


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

[Package lattice version 0.15-4 Index]