emulator (version 1.1-5)

emulator-package: Emulation of computer code output

Description

This package allows one to estimate the output of a computer program, as a function of the input parameters, without actually running it. The computer program is assumed to be a Gaussian process, whose parameters are estimated using Bayesian techniqes that give a PDF of expected program output. This PDF is conditional on a training set of runs, each consisting of a point in parameter space and the model output at that point. The emphasis is on complex codes that take weeks or months to run, and that have a large number of undetermined input parameters; many climate prediction models fall into this class. The emulator essentially determines Bayesian a-postiori estimates of the PDF of the output of a model, conditioned on results from previous runs and a user-specified prior linear model. A working example is given in the help page for function interpolant(), which should be the users's first point of reference.

Details

ll{ Package: emulator Type: Package Version: 1.0 Date: 2007-05-02 License: GPL }

The primary function of the package is interpolant().

References

• J. Oakley 1999.Bayesian uncertainty analysis for complex computer codes, PhD thesis, University of Sheffield
• J. Oakley and A. O'Hagan, 2002.Bayesian Inference for the Uncertainty Distribution of Computer Model Outputs, Biometrika 89(4), pp769-784
• R. K. S. Hankin 2005.Introducing BACCO, an R bundle for Bayesian analysis of computer code output, Journal of Statistical Software, 14(16)

Examples

# The following example takes a toy dataframe (toy), which represents an
#  experimental design.  Variable d contains observations at points in a
#  six dimensional parameter space specified by the rows of toy.
#  Function interpolant() is then called to estimate what the
#  observation would be at a point that has no direct observation.


data(toy)
d <- c(11.05, 7.48, 12.94, 14.91, 11.34, 5.0, 11.83, 11.761, 11.62, 6.70)
fish <- rep(1,6)
x <- rep(0.5, 6)
interpolant(x, d, toy, scales=fish,give=TRUE)