getCovariate.corStruct {nlme}

Extract corStruct Object Covariate

Description

This method function extracts the covariate(s) associated with object.

Usage

## S3 method for class 'corStruct'
getCovariate(object, form, data)

Arguments

object

an object inheriting from class corStruct representing a correlation structure.

form

this argument is included to make the method function compatible with the generic. It will be assigned the value of formula(object) and should not be modified.

data

an optional data frame in which to evaluate the variables defined in form, in case object is not initialized and the covariate needs to be evaluated.

Value

when the correlation structure does not include a grouping factor, the returned value will be a vector or a matrix with the covariate(s) associated with object. If a grouping factor is present, the returned value will be a list of vectors or matrices with the covariate(s) corresponding to each grouping level. For spatial correlation structures, this extracts the distances implied by the covariates, and excludes 1-observation groups.

Author(s)

José Pinheiro and Douglas Bates [e-mail]

References

Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer.

See Also

getCovariate

Examples

cs1 <- corAR1(form = ~ 1 | Subject)
getCovariate(cs1, data = Orthodont)