| fix.curved {ergm} | R Documentation |
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.
## S3 method for class 'ergm' fix.curved(object, ...) ## S3 method for class 'formula' fix.curved(object, theta, response = NULL, ...)
object |
An |
theta |
Curved model parameter configuration. |
response |
For valued ERGM, an edge attribute used as the response variable. |
... |
Unused at this time. |
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(alpha=.5,fixed=FALSE),
control=control.ergm(MCMLE.maxit=3))
summary(gest)
# A statistic for esp(1),...,esp(16)
simulate(gest,statsonly=TRUE)
tmp<-fix.curved(gest)
tmp
# A gwesp() statistic only
simulate(tmp$formula, coef=tmp$theta, statsonly=TRUE)