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Last data update: 2014.03.03

R: Functions for Querying, Validating and Extracting from ERGM...

formula.utils

R Documentation

Functions for Querying, Validating and Extracting from ERGM Formulas

Description

These are all functions that are generally not called directly by users, but may be employed by other depending packages.

Usage

nonsimp.update.formula(object, new, ..., from.new = FALSE)

term.list.formula(rhs, sign = +1)

append.rhs.formula(object, newterms, keep.onesided = FALSE)

Arguments

`object`	formula object to be updated
`new`	new formula to be used in updating
`from.new`	logical or character vector of variable names. controls how environment of formula gets updated.
`rhs`	a formula-style call containing the right hand side of formula, obtained by `fmla[[3]]` for a two-sided formula and `fmla[[2]]` for a one-sided formula.
`sign`	an internal parameter used by `term.list.formula` when calling itself recursively
`newterms`	list of terms (names) to append to the formula
`keep.onesided`	if the initial formula is one-sided, keep it whether to keep it one-sided or whether to make the initial formula the new LHS
`...`	Additional arguments. Currently unused.

Details

nonsimp.update.formula is a reimplementation of update.formula that does not simplify. Note that the resulting formula's environment is set as follows. If from.new==FALSE, it is set to that of object. Otherwise, a new sub-environment of object, containing, in addition, variables in new listed in from.new (if a character vector) or all of new (if TRUE).
term.list.formula returns a list containing terms in a given formula, handling + and - operators and parentheses, and keeping track of whether a term has a plus or a minus sign.
append.rhs.formula appends a list of terms to the RHS of a formula. If the formula is one-sided, the RHS becomes the LHS, if keep.onesided==FALSE (the default).

Value

terms.list.formula returns a list of formula terms, each of witch having an additional attribute "sign".

nonsimp.update.formula and append.rhs.formula each return an updated formula object

Examples

## append.rhs.formula

append.rhs.formula(y~x,list(as.name("z1"),as.name("z2"))) # y~x+z1+z2
append.rhs.formula(~y,list(as.name("z"))) # y~z
append.rhs.formula(~y+x,list(as.name("z"))) # y+x~z
append.rhs.formula(~y,list(as.name("z")),TRUE) # ~y+z