swh:1:snp:e520bf41b0e99213acde680a9d87fadac1aee079
Tip revision: fd4911aa390fd49ddab92bd139bbbf35422e32e5 authored by Martin Schlather on 06 February 2020, 05:20:37 UTC
version 3.3.8
version 3.3.8
Tip revision: fd4911a
RMdagum.Rd
\name{RMdagum}
\alias{RMdagum}
\title{Dagum Covariance Model Family}
\description{
\command{\link{RMdagum}} is a stationary isotropic covariance model.
The corresponding covariance function only depends on the distance \eqn{r \ge 0}{r \ge 0} between
two points and is given by
\deqn{C(r) = 1-(1+r^{-\beta})^{\frac{-\gamma}{\beta}}.}{C(r) = 1-(1+r^(-\beta))^(-\gamma / \beta).}
The parameters \eqn{\beta}{\beta} and \eqn{\gamma}{\gamma} can be varied in the intervals \eqn{(0,1]}{(0,1]}
and \eqn{(0,1)}{(0,1)}, respectively.
}
\usage{
RMdagum(beta, gamma, var, scale, Aniso, proj)
}
\arguments{
\item{beta}{numeric in \eqn{(0,1]}{(0,1]}}
\item{gamma}{numeric in \eqn{(0,1)}{(0,1)}}
\item{var,scale,Aniso,proj}{optional arguments; same meaning for any
\command{\link{RMmodel}}. If not passed, the above
covariance function remains unmodified.}
}
\details{Like the generalized Cauchy model the Dagum family can be used
to model fractal dimension and Hurst effect. For a comparison of these
see Berg, C. and Mateau, J. and Porcu, E. (2008). This paper also
establishes valid parameter choices for the Dagum family, but be
careful because therein the model is parameterized differently.
}
\value{
\command{\link{RMdagum}} returns an object of class \code{\link[=RMmodel-class]{RMmodel}}.
}
\references{
\itemize{
\item Berg, C. and Mateau, J. and Porcu, E. (2008)
The dagum family of isotropic correlation functions.
\emph{Bernoulli} \bold{14}(4), 1134--1149.
}
}
\me
\seealso{
\command{\link{RMmodel}},
\command{\link{RFsimulate}},
\command{\link{RFfit}}.
}
\keyword{spatial}
\keyword{models}
\examples{\dontshow{StartExample()}
RFoptions(seed=0) ## *ANY* simulation will have the random seed 0; set
## RFoptions(seed=NA) to make them all random again
model <- RMdagum(beta=0.5, gamma=0.5, scale=0.2)
x <- seq(0, 10, 0.02)
plot(model)
plot(RFsimulate(model, x=x))
\dontshow{FinalizeExample()}}