Get/set formula components.

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Description

f_rhs extracts the righthand side, f_lhs extracts the lefthand side, and f_env extracts the environment. All functions throw an error if f is not a formula.

Usage

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f_rhs(f)

f_rhs(x) <- value

f_lhs(f)

f_lhs(x) <- value

f_env(f)

f_env(x) <- value

Arguments

f, x

A formula

value

The value to replace with.

Value

f_rhs and f_lhs return language objects (i.e. atomic vectors of length 1, a name, or a call). f_env returns an environment.

Examples

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f_rhs(~ 1 + 2 + 3)
f_rhs(~ x)
f_rhs(~ "A")
f_rhs(1 ~ 2)

f_lhs(~ y)
f_lhs(x ~ y)

f_env(~ x)