Convert a curved ERGM into a form suitable as initial values for the same ergm.

Description

The generic enformulate.curved converts an ergm object or formula of a model with curved terms to the variant in which the curved parameters embedded into the formula and are removed from the parameter vector. This is the form required by ergm calls.

Usage

## S3 method for class 'ergm'
enformulate.curved(object, ...)
## S3 method for class 'formula'
enformulate.curved(object, theta, response=NULL, ...)

Arguments

Details

Because of a current kludge in ergm, output from one run cannot be directly passed as initial values (control.ergm(init=)) for the next run if any of the terms are curved. One workaround is to embed the curved parameters into the formula (while keeping fixed=FALSE) and remove them from control.ergm(init=).

This function automates this process for curved ERGM terms included with the ergm package. It does not work with curved terms not included in ergm.

Value

A list with the following components:

See Also

ergm, simulate.ergm

Examples

data(sampson)
gest<-ergm(samplike~edges+gwesp(alpha=.5, fixed=FALSE), 
    control=control.ergm(MCMLE.maxit=1))
# Error:
gest2<-try(ergm(gest$formula, control=control.ergm(init=coef(gest), MCMLE.maxit=2)))
print(gest2)

# Works:
tmp<-enformulate.curved(gest)
tmp
gest2<-try(ergm(tmp$formula, control=control.ergm(init=tmp$theta, MCMLE.maxit=2)))
summary(gest2)