** Utilities for Formulas, Expressions, Calls, Assignments and Other R Objects**

These utilities facilitate the programmatic manipulations of formulas, expressions, calls, names, symbols and other R language objects. These objects all share the same structure: a left-hand side (lhs), an operator (op) and right-hand side (rhs). This packages provides methods for accessing and modifying this structures as well as extracting and replacing names and symbols from these objects.

It is easiest to understand through the [#Examples].

`install.packages('formula.tools')`

`devtools::install_github("decisionpatterns/formula.tools")`

: get/set the left-hand side of an object`lhs`

: get/set the right-hand side of an object`rhs`

: get/set the operator of an object`op`

: like`get.vars`

`base::all.vars`

except all symbols (e.g.`.`

) can be interpolated from data, so that things like`y ~ .`

can return the correct values.:`lhs.vars`

`get.vars`

on lhs of the object:`rhs.vars`

`get.vars`

on rhs of the object

: get the terms from an object by interpolating special symbols (e.g.`terms`

`.`

) using a data set data. Extends`stats::terms()`

: split (mathematical) terms into an expression vector without interpolating special symbols (e.g.`split_terms`

`.`

)

Formula terms and operators can be accessed or changed.

```
## Get parts of formula
form <- y ~ x
lhs(form) # y
lhs(form) <- quote(t)
form # t ~ x
rhs(form) # x
rhs(form) <- 1
form # t ~ 1
## Get variables (names)
form <- y ~ m*x + b
get.vars(form) # "y" "m" "x" "b"
lhs.vars(form) # "y"
rhs.vars(form) # "m" "x" "b"
## Split terms
terms(form)
split_terms(form) # expression(Species ~ . - Sepal.Length)
split_terms( quote(a+(b+(c+d))), recursive=TRUE ) # expression(a, b, c, d)
```