Compute Allowed Changes in Adding to or Dropping from a...

factor.scope {stats}

R Documentation

Compute Allowed Changes in Adding to or Dropping from a Formula

Description

add.scope and drop.scope compute those terms that can be individually added to or dropped from a model while respecting the hierarchy of terms.

Usage

add.scope(terms1, terms2)

drop.scope(terms1, terms2)

factor.scope(factor, scope)

Arguments

`terms1`	the terms or formula for the base model.
`terms2`	the terms or formula for the upper (`add.scope`) or lower (`drop.scope`) scope. If missing for `drop.scope` it is taken to be the null formula, so all terms (except any intercept) are candidates to be dropped.
`factor`	the `"factor"` attribute of the terms of the base object.
`scope`	a list with one or both components `drop` and `add` giving the `"factor"` attribute of the lower and upper scopes respectively.

Details

factor.scope is not intended to be called directly by users.

Value

For add.scope and drop.scope a character vector of terms labels. For factor.scope, a list with components drop and add, character vectors of terms labels.

Examples

add.scope( ~ a + b + c + a:b,  ~ (a + b + c)^3)
# [1] "a:c" "b:c"
drop.scope( ~ a + b + c + a:b)
# [1] "c"   "a:b"

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