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\name{contrast.bayes}
\alias{contr.bayes.ordered}
\alias{contr.bayes.unordered}
\title{Contrast Matrices}
\description{
Return a matrix of contrasts used in \code{\link{bayesglm}}.
}
\usage{
contr.bayes.unordered(n, base = 1, contrasts = TRUE)
contr.bayes.ordered (n, scores = 1:n, contrasts = TRUE)
}
\arguments{
\item{n}{a vector of levels for a factor, or the number of levels.}
\item{base}{an integer specifying which group is considered the baseline
group. Ignored if \code{contrasts} is \code{FALSE}.}
\item{contrasts}{a logical indicating whether contrasts should be computed.}
\item{scores}{the set of values over which orthogonal polynomials are to be
computed.}
}
\details{
These functions are adapted from \code{contr.treatment} and \code{contr.poly}
in \code{\link{stats}} package. The purpose for these functions are to keep
the baseline levels of categorical variables and thus to suit the use of
\code{\link{bayesglm}}.
\code{contr.bayes.unordered} is equivalent to \code{contr.treatment} whereas
\code{contr.bayes.ordered} is equivalent to \code{contr.poly}.
}
\author{Yu-Sung Su \email{suyusung@tsinghua.edu.cn}}
\seealso{
\code{\link{C}},
\code{\link{contr.helmert}},
\code{\link{contr.poly}},
\code{\link{contr.sum}},
\code{\link{contr.treatment}};
\code{\link{glm}},
\code{\link{aov}},
\code{\link{lm}},
\code{\link{bayesglm}}.
}
\examples{
cat.var <- rep(1:3, 5)
dim(contr.bayes.unordered(cat.var))
# 15*15 baseline level kept!
dim(contr.treatment(cat.var))
# 15*14
}
\keyword{design}
\keyword{regression}
\keyword{array}
\keyword{manip}
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