This package provides functionality for producing variance dispersion graphs (VDGs), fraction-of-design (FDS) plots and related graphics for assessing the prediction variance properties of experimental designs. Random sampling is used to assess the distribution of the prediction variance throughout the design region. Multiple design and/or model formulae can be assessed at the same time. Graphics are produced by the ggplot2 package.
The workhorse function in the package is
spv, which takes lists of
experimental designs and / or model formulae and produces samples throughout the design region
at which the prediction variance is evaluated. Depending on the type of input for the
spv creates output objects of S3 classes
spvlistforlist. The graphical output are
obtained with the
plot methods of these classes, and the
can be used to control the type of plots produced.
The design regions allowed for are typically spherical or cuboidal in nature, but the
keepfun argument to
spv can be used for rejection sampling. In this way
nonstandard design regions can be allowed for. See also the
type argument of
The output from the
plot methods for objects created by
typically named lists of graphical objects created by ggplot2. These are best stored in an
object and recreated by printing the required plot. Storing such graphical objects also enables
post-hoc manipulation of the plots, such as changing the background colour by using
Pieter C. Schoonees <email@example.com>
Pieter C. Schoonees, Niel J. le Roux, Roelof L.J. Coetzer (2016). Flexible Graphical Assessment of Experimental Designs in R: The vdg Package. Journal of Statistical Software, 74(3), 1-22. doi: 10.18637/jss.v074.i03.