getCovariate.varFunc {nlme} | R Documentation

## Extract varFunc Covariate

### Description

This method function extracts the covariate(s) associated with the variance function represented by `object`, if any is present.

### Usage

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

### Arguments

`object` | an object inheriting from class `varFunc`, representing a variance function structure.
`form` | an optional formula specifying the covariate to be evaluated in `object`. Defaults to `formula(object)`.
`data` | some methods for this generic require a `data` object. Not used in this method.

### Value

if `object` has a `covariate` attribute, its value is returned; else `NULL` is returned.

### Author(s)

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

### See Also

`covariate<-.varFunc`

### Examples

    data(Orthodont)
    vf1 <- varPower(1.1, form = ~age)
    covariate(vf1) <- Orthodont[["age"]]
    getCovariate(vf1)

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