# factor.scope

##### Compute Allowed Changes in Adding to or Dropping from a Formula

`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.

- Keywords
- models

##### 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.

##### See Also

##### Examples

`library(stats)`

```
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"
```

*Documentation reproduced from package stats, version 3.3.3, License: Part of R 3.3.3*

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