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)

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

`corExp`

, `plot.Variogram`

### Examples

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

[Package

*nlme* version 3.1-66

Index]