Package 'formula.tools'

Invert multiple elements of a multiple element object

Description

Invert multiple elements of a multiple element object

Usage

.invert.single(x)

.invert.plural(x)

Arguments

x	object to invert from

See Also

.invert.single

---

Converts a formula to character

Description

Convers a formula to character representaion

Usage

## S3 method for class 'formula'
as.character(x, ...)

Arguments

x	formula object
...	further arguments passed to or from other methods.

Details

Coerces formula to a character by deparsing.

Value

A character vector

Author(s)

Christopher Brown

See Also

deparse

Examples

as.character( y ~ mx +  b )

## The function is currently defined as
function(x)
  Reduce( paste, deparse(x) )

---

Get the environment

Description

Get the environment

Usage

env(x)

## S3 method for class 'formula'
env(x)

Arguments

x	object to get environoment from

Details

S3 returns the environment associated with an object.

For a formula object, 'env' returns the environment in the '.Environment' attribute.

Value

Environment

Examples

env( lhs ~ rhs )

---

Manipulate the component parts of formulas, expressions, calls, name/symbols and list and vectors of such objects.

Description

lhs, rhs, op, and op.type retrieve the various parts of R formulas, calls, expressions, names/symbols. These functions were designed to greatly facilitate symbolic manupulation using native R objects. Also provided are methods to handle list of these objects.

Usage

lhs(x, ...)

## S4 method for signature 'call'
lhs(x)

## S4 method for signature 'formula'
lhs(x)



## S4 method for signature 'expression'
lhs(x, ...)

## S4 method for signature 'list'
lhs(x, ...)

lhs(x) <- value

## S4 replacement method for signature 'call'
lhs(x) <- value

## S4 replacement method for signature 'formula'
lhs(x) <- value



.replace.lhs.plural(x, value)

## S4 replacement method for signature 'expression'
lhs(x) <- value

## S4 replacement method for signature 'list'
lhs(x) <- value

op(x)

## S4 method for signature 'formula'
op(x)

## S4 method for signature 'call'
op(x)

## S4 method for signature 'name'
op(x)

## S4 method for signature 'expression'
op(x)

## S4 method for signature 'list'
op(x)



op(x) <- value

## S4 replacement method for signature 'call'
op(x) <- value

## S4 replacement method for signature 'formula'
op(x) <- value



.replace.op.plural(x, value)

## S4 replacement method for signature 'expression'
op(x) <- value

## S4 replacement method for signature 'list'
op(x) <- value

rhs(x, ...)

.rhs.singular(x)

## S4 method for signature 'call'
rhs(x)

## S4 method for signature 'formula'
rhs(x)



## S4 method for signature 'expression'
rhs(x, ...)

## S4 method for signature 'list'
rhs(x, ...)

rhs(x) <- value

.replace.rhs.singular(x, value)

## S4 replacement method for signature 'call'
rhs(x) <- value

## S4 replacement method for signature 'formula'
rhs(x) <- value



.replace.rhs.plural(x, value)

## S4 replacement method for signature 'expression'
rhs(x) <- value

## S4 replacement method for signature 'list'
rhs(x) <- value

Arguments

x	object from where to get/set the lhs/rhs
...	arguments passed to additional methods
value	the value to set for the lhs/rhs

Details

lhs retrieves the left-hand side rhs retrieves the right-hand side op retrieves the operation op.type returns the type operator

There are also functions lhs.vars and rhs.vars. Like all.vars , these functions interpret the variables on the left-hand and right-hand sides respectively.

These are simple functions for extracting the left-hand side, right-hand side, operator and operator type from formulas, expressions, calls, names/symbols and list containing these objects. lhs, rhs are only defined for formulas and calls ( and list and expressions ) that are defined with either one of the relational or tilde ('~') operators. If the object does not contain one of these operators, it will fail with a warning.

The defined operator types are defined by the operator.tools package: See operators and setOperator

The lhs.vars and rhs.vars methods, return the variables used on the lhs and rhs, respectively. If special formula variables are used, such as '.', a data.frame or environment must also be provided such that the variable list may be properly infered.

Value

Value depends on the argument.

Note

Methods for the non-standard "<-" class exist and are not included in the usage documentation because CRAN does not support S4 documentation for this class.

Author(s)

Christopher Brown

See Also

terms, all.vars, all.names, operators

Examples

# FORMULA
  f <- A + B ~ C + D
  lhs(f)
  lhs(f) <- quote( E / F )

  rhs(f)
  rhs(f) <- quote( G + H ) 
  op(f)
  op(rhs(f))
  op( quote(A) )  # NULL: 
  op.type(f)

  # ONE-SIDED FORMULA
  f <- ~ A   # 
  lhs(f)     # NULL
  rhs(f)     # A


  # EXPRESSION
  e <- expression( A + B == C + D )
  lhs(e)
  rhs(e)
  op(e)
  op.type(e)


  # CALL
  c <- quote( A + B > C + D )
  lhs(c)
  lhs(c) <- quote(E)
  rhs(c)

  op(c)
  op.type(c)

  # ASSIGNMENT 
  a  <- quote( A <- B ) 
  lhs(a)
  rhs(a) 
  op(a)
  op.type(a)

---

Get variable (names) from various R objects

Description

get.vars extracts variable names from various R objects such as formulas, expressions, calls, symbols, etc. It is very similar to all.vars except that all symbols, etc. are interpolated to the names of variables.

Usage

get.vars(x, data = NULL, ...)

## S4 method for signature 'formula,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'call,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'expression,missing'
get.vars(x, data = NULL, ...)

## S4 method for signature 'name,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'ANY,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature ''NULL',ANY'
get.vars(x, data = NULL, ...)

lhs.vars(x, ...)

.lhs.vars(x, ..., data = NULL)

## S4 method for signature 'formula'
lhs.vars(x, ..., data = NULL)

## S4 method for signature 'call'
lhs.vars(x, ..., data = NULL)

## S4 method for signature 'expression'
lhs.vars(x, ...)

rhs.vars(x, ...)

.rhs.vars(x, ..., data = NULL)

## S4 method for signature 'formula'
rhs.vars(x, ..., data = NULL)

## S4 method for signature 'call'
rhs.vars(x, ..., data = NULL)

## S4 method for signature 'expression'
rhs.vars(x, ...)

Arguments

x	object to extract vars from.
data	data set/list or environment on which the names are defined
...	arguments passed to subsequent functions get.vars and variant get the variables from objects optionally interpreting on . on the data. This is useful, for example, when you wish to know what data is used based on a given formula. Methods/functions beginning with . are not exported

Value

character vector of variables names in order that they appear in x.

See Also

all.vars

Examples

get.vars( Species ~ ., iris )
  get.vars( quote( Sepal.Length * Sepal.Width ), iris )

---

invert

Description

Invert the operators in an object, usually a formula or expression

Usage

invert(x, ...)

## S4 method for signature 'call'
invert(x)

## S4 method for signature 'expression'
invert(x)

Arguments

x	function for invert
...	additional arguments passed other functions invert is a S4 generic method for inverting relational operators, i.e. functions prefixed with a . are not exported and should probably not be called directly

Value

The operand is returned with the relational operators inverted.

Author(s)

Christopher Brown

See Also

op, op.type

Examples

invert( quote( A >  5 ) )
  invert( quote( A >= 5 ) )
  invert( quote( A <  5 ) )
  invert( quote( A <= 5 ) )
  invert( quote( A == 5 ) )
  invert( quote( A != 5 ) )
  invert( quote( A %in% lettters[1:5] ) )
  invert( quote( A %!in% letters[1:5] ) )

---

Determine if an object is one- or two-sided. Test whether a object (typically formula, call or expression) is one- (e.g. ~x) or two-sided (e.g. x~y).

Description

Determine if an object is one- or two-sided.

Test whether a object (typically formula, call or expression) is one- (e.g. ~x) or two-sided (e.g. x~y).

Usage

is.one.sided(x, ...)

## S4 method for signature 'formula'
is.one.sided(x, ...)

## S4 method for signature 'call'
is.one.sided(x, ...)



## S4 method for signature 'expression'
is.one.sided(x, ...)

## S4 method for signature 'list'
is.one.sided(x, ...)

## S4 method for signature 'ANY'
is.one.sided(x, ...)

is.two.sided(x, ...)

## S4 method for signature 'formula'
is.two.sided(x, ...)

## S4 method for signature 'call'
is.two.sided(x, ...)



## S4 method for signature 'expression'
is.two.sided(x, ...)

## S4 method for signature 'list'
is.two.sided(x, ...)

## S4 method for signature 'ANY'
is.two.sided(x, ...)

Arguments

x	object to test for one-sidedness.
...	arguments passed to called functions

Details

These functions detect whether the formula is single- (unary) or double- sided. They work on formulas, expression, calls, assignments, etc.

is.single.sided and is.unary are alias for is.single.sided. is.double.sided and is.binary are aliases for is.two.sided.

Value

logical; whether x is an object is one-sided or two-sided formula.

Note

Methods for the "<-" class exist and are not included in the usage documentation because CRAN does not support S4 documentation for this class.

Examples

form <- y ~ x 

is.one.sided(form)
# is.single.sided(form)
# is.unary(form) 

is.two.sided(form)
# is.double.sided(form)
# is.binary(form)

---

Get the operator type used in an call, formula, expression, etc.

Description

Get the operator type used in an call, formula, expression, etc.

Usage

op.type(x)

## S4 method for signature 'call'
op.type(x)

## S4 method for signature 'formula'
op.type(x)



## S4 method for signature 'ANY'
op.type(x)

## S4 method for signature 'expression'
op.type(x)

## S4 method for signature 'list'
op.type(x)

Arguments

x	object from which to extract the operator type

Value

a character vector of the operator type(s)

See Also

op, operator.type

---

Split object into terms

Description

Split formulas, call and expressions into terms.

Usage

split_terms(x, recursive = FALSE)

Arguments

x	object to split terms from
recursive	logical; whether to split terms recursively in parenthetical enclosed terms (depth-first). (Default: FALSE)

Details

Unlike the [terms()] function, 'split_terms' does not use [stats::terms()] and instead just splits 'x' into an **expression vector** of terms. (Terms are the mathematical notion of terms). The signs of the terms are preserved.

If 'recursive' is 'TRUE', splitting occurs recursively, i.e. parsing of the input descends into parenthetical expressions '(...)'.

See **examples**.

Value

experession vector of terms

References

* [SO: How to split a formula](https://stackoverflow.com/questions/39155701/how-to-split-a-formula-in-r)

See Also

* [terms()]

Examples

split_terms(1)                   # 1
  split_terms( quote(a) )          # a     
  split_terms( quote(-a) )         # -a   
  split_terms( quote(a+1) )        # a, 1
  split_terms( quote(1+a) )        # 1, a
  split_terms( quote(-1+a) )       # -1, a
  split_terms( quote(-1-a) )
  
  split_terms( quote(a+b+c) )      # a,b,c
  split_terms( quote((a+b)+1) )    # (a+b),1
  split_terms( quote((a+b)+1), recursive=TRUE )    # a,b,1
  split_terms( quote((a-b)+1), recursive=TRUE )    # a,-b,1
  split_terms( quote(-a) )         # -a
  
  split_terms( quote(a-1) )        # a, -1
  split_terms( quote(-a-1))        # -a, -1
  split_terms( quote( -(a+1) ) )   # -(a+1)
  split_terms( quote( -(a+1) ), recursive=TRUE )  # -a,-1
  
  split_terms( quote( ---a ))
  split_terms( quote( -(a+(b-(c+d)))), recursive=TRUE )

---

terms

Description

terms method for call and expression objects

Usage

## S3 method for class 'call'
terms(x, ...)

## S3 method for class 'expression'
terms(x, ...)

Arguments

x	A call object
...	Arguments passed to terms.formula This S3 method returns a terms object for a call methods using a dispatch to terms.formula . The terms are generated by making a rhs only call to terms.formula . data is only needed and must be explicitly specified, i.e. data = if there are special elements such as '.'. Otherwise the data argument is unused. Some edge cases may not be supported.

Value

A terms object. See terms.object for details.

Author(s)

Christopher Brown

See Also

• stats::terms.object()

• stats::terms.formula()

Examples

terms( quote( A + B ) )

    data(iris) 
    x <- terms( quote( . - Species ) , data=iris )

---

toggle the sign of an expression

Description

toggle the sign of an expression

Usage

toggle.sign(x)

Arguments

x	expression

Details

'toggle.sign' changes the sign of an expression for '+' tp '-' and visa-versa.

Examples

toggle.sign(1:3)
  toggle.sign( quote(a) )
  toggle.sign( quote(-a) )
  
  exp <- expression( a, -b, -(a-b) )
  toggle.sign(exp)

---