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\title{Utilities for formulas}
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\alias{getCovariateFormula}
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\alias{getGroups,data.frame,formula-method}
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\alias{getGroups,groupedData-method}
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\alias{getGroups,groupedData,missing-method}
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\alias{getGroupsFormula}
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\alias{getGroupsFormula,ANY-method}
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\alias{getResponseFormula}
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These generic functions extract sub-formulas or values of components
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from a formula/data pair.
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getCovariate(object, form, data)
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getCovariateFormula(object)
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getGroups(object, form, level, data, sep, \dots)
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getGroupsFormula(object, asList, sep)
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getResponse(object, form)
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getResponseFormula(object)
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splitFormula(form, sep)
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\item{object}{a formula or an object that can provide a formula}
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\item{form}{an optional formula with a conditioning expression on its
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right hand side (i.e. an expression involving the \code{|}
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operator). Defaults to \code{formula(object)}.}
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\item{level}{a positive integer vector with the level(s) of grouping to
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be used when multiple nested levels of grouping are present. This
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argument is optional for most methods of this generic function and
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defaults to all levels of nesting.}
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\item{data}{a data frame in which to interpret the variables named in
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\code{form}. Optional for most methods.}
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\item{asList}{an optional logical value. If \code{TRUE} the returned
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value with be a list of formulas; else, if \code{FALSE} the returned
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value will be a one-sided formula. Defaults to \code{FALSE}.}
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\item{sep}{character, the separator to use between group levels when
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multiple levels are collapsed. Defaults to \code{'/'}.}
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\item{pos}{the integer index of the component of the formula to
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return. Defaults to \code{2}.}
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\item{\dots}{Optional arguments that are passed to some methods. None
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\code{getGroupsFormula} returns a one-sided formula, or a list of
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one-sided formulas, giving the grouping structure associated with
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\code{formula(object)}. If no conditioning expression is present in
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\code{formula(object)} a \code{NULL} value is returned.
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form = resp ~ cov1 + cov2 | grp1/grp2
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getResponseFormula(form)
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getCovariateFormula(form)
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getGroupsFormula(form)
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getGroupsFormula(form, asList = TRUE)
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man/formulas.Rd
