is.curved {ergm}

Testing for curved exponential family

Description

These functions test whether an ERGM fit, formula, or some other object represents a curved exponential family.

The method for NULL always returns FALSE by convention.

Usage

is.curved(object, ...)

## S3 method for class ''NULL''
is.curved(object, ...)

## S3 method for class 'formula'
is.curved(object, response = NULL, basis = NULL, ...)

## S3 method for class 'ergm'
is.curved(object, ...)

Arguments

object

An ergm object or an ERGM formula.

...

Arguments passed on to lower-level functions.

response

Either a character string, a formula, or NULL (the default), to specify the response attributes and whether the ERGM is binary or valued. Interpreted as follows:

NULL

Model simple presence or absence, via a binary ERGM.

character string

The name of the edge attribute whose value is to be modeled. Type of ERGM will be determined by whether the attribute is logical (TRUE/FALSE) for binary or numeric for valued.

a formula

must be of the form NAME~EXPR|TYPE (with | being literal). EXPR is evaluated in the formula's environment with the network's edge attributes accessible as variables. The optional NAME specifies the name of the edge attribute into which the results should be stored, with the default being a concise version of EXPR. Normally, the type of ERGM is determined by whether the result of evaluating EXPR is logical or numeric, but the optional TYPE can be used to override by specifying a scalar of the type involved (e.g., TRUE for binary and 1 for valued).

basis

See ergm().

Details

Curvature is checked by testing if all model parameters are canonical.

Value

TRUE if the object represents a curved exponential family; FALSE otherwise.