lme4 (version 0.8-3)

formulas: Utilities for formulas

Description

These generic functions extract sub-formulas or values of components from a formula/data pair.

Usage

getCovariate(object, form, data)
getCovariateFormula(object)
getGroups(object, form, level, data, sep, ...)
getGroupsFormula(object, asList, sep)
getResponse(object, form)
getResponseFormula(object)
subFormula(form, pos)
splitFormula(form, sep)

Arguments

object

a formula or an object that can provide a formula

form

an optional formula with a conditioning expression on its right hand side (i.e. an expression involving the | operator). Defaults to formula(object).

level

a positive integer vector with the level(s) of grouping to be used when multiple nested levels of grouping are present. This argument is optional for most methods of this generic function and defaults to all levels of nesting.

data

a data frame in which to interpret the variables named in form. Optional for most methods.

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. Defaults to '/'.

pos

the integer index of the component of the formula to return. Defaults to 2.

...

Optional arguments that are passed to some methods. None used at present.

Value

• getGroupsFormula returns a one-sided formula, or a list of one-sided formulas, giving the grouping structure associated with formula(object). If no conditioning expression is present in formula(object) a NULL value is returned.

Examples

form = resp ~ cov1 + cov2 | grp1/grp2
getResponseFormula(form)
getCovariateFormula(form)
getGroupsFormula(form)
getGroupsFormula(form, asList = TRUE)