Convert a curved ERGM into a corresponding "fixed" ERGM.
The generic fix.curved converts an ergm object or
formula of a model with curved terms to the variant in which the curved
parameters are fixed. Note that each term has to be treated as a special
case.
fix.curved(object, ...) ## S3 method for class 'ergm' fix.curved(object, ...) ## S3 method for class 'formula' fix.curved(object, theta, response = NULL, ...)
object |
An |
... |
Unused at this time. |
theta |
Curved model parameter configuration. |
response |
Name of the edge attribute whose value is to be
modeled in the valued ERGM framework. Defaults to |
Some ERGM terms such as gwesp and gwdegree have
two forms: a curved form, for which their decay or similar parameters are to
be estimated, and whose canonical statistics is a vector of the term's
components (esp(1), esp(2), ... and
degree(1), degree(2), ..., respectively) and
a "fixed" form where the decay or similar parameters are fixed, and whose
canonical statistic is just the term itself. It is often desirable to fit a
model estimating the curved parameters but simulate the "fixed" statistic.
This function thus takes in a fit or a formula and performs this mapping,
returning a "fixed" model and parameter specification. It only works for
curved ERGM terms included with the ergm
package. It does not work with curved terms not included in ergm.
A list with the following components:
formula |
The "fixed" formula. |
theta |
The "fixed" parameter vector. |
data(sampson)
gest<-ergm(samplike~edges+gwesp(decay=.5,fixed=FALSE),
control=control.ergm(MCMLE.maxit=3, MCMC.burnin=1024, MCMC.interval=128))
summary(gest)
# A statistic for esp(1),...,esp(16)
simulate(gest,output="stats")
tmp<-fix.curved(gest)
tmp
# A gwesp() statistic only
simulate(tmp$formula, coef=tmp$theta, output="stats")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.