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\name{RMma}
\alias{RMma}
\title{Ma operator}
\description{
\command{\link{RMma}} is a univariate stationary covariance model
depending on a univariate stationary covariance model.
The corresponding covariance function only depends on the difference
\eqn{h}{h} between two points and is given by
\deqn{C(h) = (\theta / (1 - (1-\theta) \phi(h)))^\alpha}{C(h) = (\theta
/ (1 - (1-\theta) * \phi(h)))^\alpha}
}
\usage{
RMma(phi, alpha, theta, var, scale, Aniso, proj)
}
\arguments{
\item{phi}{a stationary covariance \command{\link{RMmodel}}.}
\item{alpha}{a numerical value; positive}
\item{theta}{a numerical value; in the interval \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{}
\value{
\command{\link{RMma}} returns an object of class \code{\link[=RMmodel-class]{RMmodel}}.
}
\references{
\itemize{
\item Ma, C. (2003)
Spatio-temporal covariance functions generated by mixtures.
\emph{Math. Geol.}, \bold{34}, 965-975.
}
}
\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 <- RMma(RMgauss(), alpha=4, theta=0.5)
x <- seq(0, 10, 0.02)
plot(model)
plot(RFsimulate(model, x=x))
\dontshow{FinalizeExample()}}
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