RandomFields (version 3.0.5)

RMuser: User Defined Function

Description

RMuser allows for a user defined covariance function, variogram model, or arbitrary function

Usage

RMuser(type, domain, isotropy, vdim, beta, fctn, fst, snd, envir,
 var, scale, Aniso, proj)

Arguments

type, domain, isotropy, vdim

see RMmodelgenerator.

beta

a fixed matrix that is multiplied to the return value of the given function; the dimension must match. Defining a vector valued function and beta as a vector, an arbitrary linear model can be defined. Estimation of beta

envir

the environment where the given function shall be evaluated

fctn, fst, snd

a user defined function and its first, second and third derivative, given as quote(myfunction(x)) or as quote(myfunction(x, y)), see Details an Examples below.

var,scale,Aniso,proj

optional parameters; same meaning for any RMmodel. If not passed, the above covariance function remains unmodified.

Value

• RMuser returns an object of class RMmodel.

See Also

RMmodel, RMmodelgenerator RFsimulate, RFfit.

Examples

set.seed(0)
## Alternatively to 'model <- RMexp()' one may define the following
## (which is, however, much slower and cannot use all features of
## RandomFields)

RFoptions(storing = FALSE)

model <- RMuser(type="positive definit", domain="single variable",
                iso="isotropic", fctn=exp(-x))
x <- y <- seq(1, 10, len=10^(1+interactive()))
plot(model)
z <- RFsimulate(RPcirculant(model), x=x, y=y, grid=TRUE)
plot(z)model <- RMnugget(var=1e-5) +
         RMuser(type="positive definit", domain="kernel",
                iso="symmetric", fctn=sum(x * y))
x <- y <- seq(1, 10, len=7^(1+interactive()))
z <- RFsimulate(model, x=x, y=y, grid=TRUE, n=6)
plot(z)