getGroupsFormula {nlme} | R Documentation |

## Extract Grouping Formula

### Description

The conditioning expression associated with `formula(object)`

(i.e. the expression after the `|`

operator) is returned either as
a named list of one-sided formulas, or a single one-sided formula,
depending on the value of `asList`

. The components of the
returned list are ordered from outermost to innermost level and are
named after the grouping factor expression.

### Usage

getGroupsFormula(object, asList, sep)

### Arguments

`object` |
any object from which a formula can be extracted. |

`asList` |
an optional logical value. If `TRUE` the returned
value with be a list of formulas; else, if `FALSE` the returned
value will be a one-sided formula. Defaults to `FALSE` . |

`sep` |
character, the separator to use between group levels when
multiple levels are collapsed. The default is `'/'` . |

### Value

a one-sided formula, or a list of one-sided formulas, with the
grouping structure associated with `formula(object)`

. If no
conditioning expression is present in `formula(object)`

a
`NULL`

value is returned.

### Author(s)

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

### See Also

`getGroupsFormula.gls`

,
`getGroupsFormula.lmList`

,
`getGroupsFormula.lme`

,
`getGroupsFormula.reStruct`

,
`getGroups`

### Examples

getGroupsFormula(y ~ x | g1/g2)

[Package

*nlme* version 3.1-66

Index]