R: Calculate Semi-variogram for a corExp Object

Variogram.corExp {nlme}

R Documentation

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 class '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.

Author(s)

José Pinheiro and Douglas Bates bates@stat.wisc.edu

References

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

Examples

stopifnot(require("stats", quietly = TRUE))
cs1 <- corExp(3, form = ~ Time | Rat)
cs1 <- Initialize(cs1, BodyWeight)
Variogram(cs1)[1:10,]

[Package nlme version 3.1-166 Index]