vdg-package {vdg}

Variance Dispersion Graphs, Fraction-of-Design-Space Plots and Variants

Description

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.

Details

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 design and formula arguments, spv creates output objects of S3 classes spv, spvlist, spvforlist or spvlistforlist. The graphical output are obtained with the plot methods of these classes, and the which argument 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 spv. The output from the plot methods for objects created by spv are 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 ggplot2's theme function.

References

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.

See Also

spv, plot.spv, and vignette(topic = "vdg").