R: Internal Functions for Querying, Validating and Extracting...

ergm.formula.utils {ergm}

R Documentation

Internal 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

ergm.getmodel(formula, nw, response = NULL, silent = FALSE, role = "static", ...)

ergm.getnetwork(form, loopswarning = TRUE)

ergm.getterms(formula)

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

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

offset.info.formula(object, response = NULL) 

remove.offset.formula(object, response = NULL)

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

Arguments

`formula`	a formula of the form `network ~ model.term(s)`
`nw`	the network of interest
`response`	charcter, name of edge attribute containing edge weights
`silent`	logical, whether to print the warning messages from the initialization of each model term; default=FALSE
`role`	A hint about how the model will be used. Used primarily for dynamic network models.
`...`	additional parameters for model formulation
`form`	same as formula, a formula of the form `'network ~ model.term(s)'`
`loopswarning`	whether warnings about loops should be printed (T or F);default=TRUE
`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

Details

The ergm.getmodel function parses the given formula, and initiliazes each ergm term via the InitErgmTerm functions to create a model.ergm object for the given network
The ergm.getnetwork function ensures that the network in a given formula is valid; if so, the network is returned; if not, execution is halted with warnings
The ergm.getterms function returns the terms of a given formula and ensures that the formula is indeed a formula with the necessary ~ operator
ergm.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.
offset.info.formula returns the offset vectors associated with a formula.
remove.offset.formula deletes all offset terms in an ERGM formula.
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

ergm.getmodel returns a 'model.ergm' object as a list containing:

formula : the formula inputted to ergm.getmodel
coef.names : a vector of coefficient names
offset : a logical vector of whether each term was "offset", i.e. fixed
terms : a list of terms and 'term components' initialized by the appropriate InitErgmTerm.X function.
network.stats0: NULL always??
etamap : the theta -> eta mapping as a list returned from <ergm.etamap>
class : the character string "model.ergm"

ergm.getnetwork returns:

the network from the formula IF (i) the formula was correctly structured and (ii) the network is found within the formula's enviornment

ergm.getterms returns:

the terms object associated with the formula and returned by the native R function terms>. see terms.object for details about the components

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

ergm.update.formula, remove.offset.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

[Package ergm version 3.4.0 Index]