lme4 (version 1.1-7)

findbars: Determine random-effects expressions from a formula

Description

From the right hand side of a formula for a mixed-effects model, determine the pairs of expressions that are separated by the vertical bar operator. Also expand the slash operator in grouping factor expressions and expand terms with the double vertical bar operator into separate, independent random effect terms.

Usage

findbars(term)

Arguments

term

a mixed-model formula

Value

• pairs of expressions that were separated by vertical bars

See Also

formula, model.frame, model.matrix.

Other utilities: mkRespMod, mkReTrms, nlformula, nobars, subbars

Examples

findbars(f1 <- Reaction ~ Days + (Days | Subject))
## => list( Days | Subject )
## These two are equivalent:% tests in ../inst/tests/test-doubleVertNotation.R
findbars(y ~ Days + (1 | Subject) + (0 + Days | Subject))
findbars(y ~ Days + (Days || Subject))
## => list of length 2:  list ( 1 | Subject ,  0 + Days | Subject)
findbars(~ 1 + (1 | batch / cask))
## => list of length 2:  list ( 1 | cask:batch ,  1 | batch)
stopifnot(identical(findbars(f1),
                    list(quote(Days | Subject))))