Variogram.corSpher {nlme} | R Documentation

## Calculate Semi-variogram for a corSpher Object

### Description

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`.

### Usage

    ## 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`.

### Author(s)

Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates bates@stat.wisc.edu

### References

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

### See Also

`corSpher`, `plot.Variogram`

### Examples

    data(BodyWeight)
    cs1 <- corSpher(15, form = ~ Time | Rat)
    cs1 <- Initialize(cs1, BodyWeight)
    Variogram(cs1)[1:10,]

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