\name{getDeviances}
\alias{getDeviances}
\title{Fetches the Deviance values from the MCMC statistics database.}
\description{
  Fetches the calculated deviance values for a given user as a coda
  \code{mcmc.list} value.
}
\usage{
getDeviances(subject = "*ALL*", iterations = numeric(0), chain = getChains())
}
\arguments{
  \item{subject}{Identifier for student or special value \code{"*ALL*"}
    for total deviance across all subjects.}
  \item{iterations}{Portion of the MCMC chains to fetch data from.}
  \item{chain}{Number of chains to use.}
}
\value{
  If only one chain, an \code{mcmc} object containing the data, if more
  than one chain, an \code{mcmc.list} object.
}
\details{
 The database used is the one referenced by the last call to
 \code{asp.dbConnect}.
}
\references{Speighelhalter, Best, Carlin and van der Linde, 2002,
  "Bayesian measures of model complexity and fit."  JRSS B, pp
  583--639.
}
\author{Russell Almond}
\note{ Deviance values were not stored in database by versions of
  StatShop prior to Beta 3.
}
\seealso{\code{\link[coda]{mcmc.list}}, \code{\link{asp.dbConnect}}}
\examples{
### This example will only run if you have the StatShop test databases
### installed on your machine.
StatShop <- Sys.getenv("STATSHOP")
if (StatShop == "") {
  warn("StatShop not installed, skipping test.")
} else {
  asp.dbConnect("parameter_recovery_test","junit")
  ## Total deviance.
  summary(getDeviances(iterations=c(101,1000)))
  ## Deviance for first simulee.
  summary(getDeviances("Simulee0",iterations=c(101,1000)))
  asp.dbDisconnect()
}
}
\keyword{database}