nlme (version 3.1-137)

Variogram.corExp: Calculate Semi-variogram for a corExp Object

Description

This method function calculates the semi-variogram values corresponding to the Exponential correlation model, using the estimated coefficients corresponding to object, at the distances defined by distance.

Usage

# S3 method for corExp
Variogram(object, distance, sig2, length.out, …)

Arguments

object

an object inheriting from class "corExp", representing an exponential spatial correlation structure.

distance

an optional numeric vector with the distances at which the semi-variogram is to be calculated. Defaults to NULL, in which case a sequence of length length.out between the minimum and maximum values of getCovariate(object) is used.

sig2

an optional numeric value representing the process variance. Defaults to 1.

length.out

an optional integer specifying the length of the sequence of distances to be used for calculating the semi-variogram, when distance = NULL. Defaults to 50.

…

some methods for this generic require additional arguments. None are used in this method.

Value

a data frame with columns variog and dist representing, respectively, the semi-variogram values and the corresponding distances. The returned value inherits from class Variogram.

References

Cressie, N.A.C. (1993), "Statistics for Spatial Data", J. Wiley & Sons.

See Also

corExp, plot.Variogram, Variogram

Examples

# NOT RUN {
stopifnot(require("stats", quietly = TRUE))
cs1 <- corExp(3, form = ~ Time | Rat)
cs1 <- Initialize(cs1, BodyWeight)
Variogram(cs1)[1:10,]
# }