Calculate the Scaled Prediction Variance (or SPV)

Description

Calculates the SPV for a sample of points in a design region of specified type. Sampling is done by calling sampler.

Usage

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spv(n, design, type = "spherical", formula, at = FALSE, keepfun, sample,
  unscaled = FALSE, ...)

## S3 method for class 'data.frame'
spv(n, design, type = c("spherical", "cuboidal", "lhs",
  "mlhs", "slhs", "rslhs", "custom"), formula, at = FALSE, keepfun, sample,
  unscaled = FALSE, ...)

## S3 method for class 'list'
spv(n, design, type = c("spherical", "cuboidal", "lhs", "mlhs",
  "slhs", "rslhs", "custom"), formula, at = FALSE, keepfun, sample,
  unscaled = FALSE, ...)

## S3 method for class 'matrix'
spv(n, design, type = c("spherical", "cuboidal", "lhs",
  "mlhs", "slhs", "rslhs", "custom"), formula, at = FALSE, keepfun, sample,
  unscaled = FALSE, ...)

Arguments

n

number of samples to take

design

a design or list of designs. Each design must be either a matrix or a data.frame or coercible to a data.frame.

type

type of sampling passed to sampler

formula

either a single model formula of a list of formulae

at

only used when type is 'spherical' or 'cuboidal'

keepfun

optional; function operating on the columns of a matrix with the same number of columns as design which return a logical value for including a specific point in the sample or not. Useful for rejection sampling for nonstandard design regions.

sample

optional; if not missing it should contain a matrix or data.frame containing points sampled over the required design region. If it is not missing, no further sampling will be done: the SPV is simply evaluated at these points.

unscaled

logical indicating whether to use the unscaled prediction variance (UPV) instead of the scale prediction variance (SPV)

...

additional arguments passed to sampler. This enables the used of user-specified sampling functions via the custom.fun argument to sampler.

Value

Object of class 'spv', 'spvlist', 'spvforlist' or 'spvlistforlist', depending on whether single designs/formulas are passed or lists of these.

Author(s)

Pieter C. Schoonees

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. \Sexpr[results=rd,stage=build]{tools:::Rd_expr_doi("10.18637/jss.v074.i03")}.

See Also

plot.spv for more examples

Examples

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# Single design (class 'spv')
library(rsm)
bbd3 <- as.data.frame(bbd(3)[,3:5])
colnames(bbd3) <- paste0("x", 1:3)
quad.3f <- formula(~(x1 + x2 + x3)^2 - x1:x2:x3)
out <- spv(n = 1000, design = bbd3, type = "spherical", formula = quad.3f)
out