update.formula

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Model Updating

update.formula is used to update model formulae. This typically involves adding or dropping terms, but updates can be more general.

Keywords
models
Usage
## S3 method for class 'formula':
update(old, new, \dots)
Arguments
old
a model formula to be updated.
new
a formula giving a template which specifies how to update.
...
further arguments passed to or from other methods.
Details

Either or both of old and new can be objects such as length-one character vectors which can be coerced to a formula via as.formula.

The function works by first identifying the left-hand side and right-hand side of the old formula. It then examines the new formula and substitutes the lhs of the old formula for any occurrence of . on the left of new, and substitutes the rhs of the old formula for any occurrence of . on the right of new. The result is then simplified via terms.formula(simplify = TRUE).

Value

  • The updated formula is returned. The environment of the result is that of old.

See Also

terms, model.matrix.

Aliases
  • update.formula
Examples
library(stats) update(y ~ x, ~ . + x2) #> y ~ x + x2 update(y ~ x, log(.) ~ . ) #> log(y) ~ x update(. ~ u+v, res ~ . ) #> res ~ u + v
Documentation reproduced from package stats, version 3.3, License: Part of R 3.3

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