\code{compar.gee} returns an object of class \code{"compar.gee"} with
the following components:
\item{call}{the function call, including the formula.}
- \code{effect.assign}{a vector of integers assigning the coefficients
+ \item{effect.assign}{a vector of integers assigning the coefficients
to the effects (used by \code{drop1}).}
\item{nobs}{the number of observations.}
\item{coefficients}{the estimated coefficients (or regression parameters).}