Calculate Semi-variogram for a corSpher Object

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

# S3 method for class 'corSpher'
Variogram(object, distance, sig2, length.out, ...)

Arguments

object: an object inheriting from class "corSpher", representing an Spherical 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.

Author

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

Examples

cs1 <- corSpher(15, form = ~ Time | Rat)
cs1 <- Initialize(cs1, BodyWeight)
Variogram(cs1)[1:10,]
#>        variog      dist
#> 1  0.09985185  1.000000
#> 2  0.22480844  2.265306
#> 3  0.34654124  3.530612
#> 4  0.46324960  4.795918
#> 5  0.57313283  6.061224
#> 6  0.67439026  7.326531
#> 7  0.76522124  8.591837
#> 8  0.84382507  9.857143
#> 9  0.90840110 11.122449
#> 10 0.95714866 12.387755