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\name{anova.clm2}
%%\alias{anova}
\alias{anova.clm2}
\alias{anova.clmm2}
\title{Likelihood ratio test of cumulative link models}
\description{
Comparison of cumulative link models in likelihood ratio tests.
The models may differ by terms in location, scale and nominal
formulae, in link, threshold function and random effect structure.
}
\usage{
\method{anova}{clm2}(object, ..., test = c("Chisq", "none"))
\method{anova}{clmm2}(object, ..., test = c("Chisq", "none"))
}
\arguments{
\item{object}{a \code{\link{clm2}} object.
}
\item{\dots}{one or more additional \code{\link{clm2}} objects.
}
\item{test}{if \code{test = "none"} the p-value for the likelihood
ratio test is suppressed.
}
}
\value{
The method returns an object of class \code{Anova} (for printing) and
\code{data.frame} with the following elements
\item{Model}{character description of the cumulative link models being
compared. Location, scale and nominal formulae are separated by
"|"s in this order.
}
\item{Resid.df}{the residual degrees of freedom
}
\item{-2logLik}{twice the negative log likelihood (proportional to the
deviance)}
\item{Test}{indication of which models are being compared.
}
\item{DF}{the difference in the degrees of freedom in the models being
compared, i.e. the degrees of freedom for the chi-squared test.
}
\item{LR stat.}{the likelihood ratio statistic.
}
\item{Pr(Chi)}{the p-value from the likelihood ratio test. Absent if
\code{test = "none"}.
}
}
\author{Rune Haubo B Christensen}
\seealso{
\code{\link[ordinal]{clm2}}, \code{\link[=addterm.clm2]{addterm}},
\code{\link[ordinal:addtermOld]{dropterm}} and
\code{\link[=anova]{anova.default}}
}
\examples{
options(contrasts = c("contr.treatment", "contr.poly"))
m1 <- clm2(SURENESS ~ PROD, scale = ~PROD, data = soup,
link = "logistic")
## anova
anova(m1, update(m1, scale = ~.-PROD))
mN1 <- clm2(SURENESS ~ 1, nominal = ~PROD, data = soup,
link = "logistic")
anova(m1, mN1)
anova(m1, update(m1, scale = ~.-PROD), mN1)
## Fit model from polr example:
if(require(MASS)) {
fm1 <- clm2(Sat ~ Infl + Type + Cont, weights = Freq, data = housing)
anova(fm1, update(fm1, scale =~ Cont))
}
}
\keyword{internal}
|
