update.formula {stats} | R Documentation |
update.formula
is used to update model formulae.
This typically involves adding or dropping terms,
but updates can be more general.
## S3 method for class 'formula': update(old, new, ...)
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. |
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 occurence
of ".
" on the left of new
, and substitutes
the rhs of the old
formula for any occurence
of ".
" on the right of new
.
The updated formula is returned.
update(y ~ x, ~ . + x2) #> y ~ x + x2 update(y ~ x, log(.) ~ . ) #> log(y) ~ x