\name{nobserved}
\alias{nobserved}
\title{Returns the number of latent variables associated with a ProficiencyModel
}
\description{

  A proficiency profile associate with a \code{\link{ProficiencyModel}}
  object is a vector of latent variable.  This function returns its length.
}
\usage{
nobserved(em)
}
\arguments{
  \item{em}{
    An object of class \code{\link{ProficiencyModel}}.
  }
}
\value{
  A scalar integer giving the expected length of the latent vector for a
  single student.
}
\references{
%% ~put references to the literature/web site here ~
}
\author{Russell Almond}

\seealso{
  \code{\link{ProficiencyModel}}
}
\examples{
Q <- matrix(c(1,0,1,1),2,2)
em1 <- new("FixedQNormalEM", Q=Q,
           zMean=c(Mechanics=0,Fluency=0),  zStd=diag(c(1,1)),
           Rmean=matrix(c(.7,.3,.3,.7),2,2), Rdf=3,
           hMean=c(1,1,.5), hStd=rep(.25,3))

stopifnot(nobserved(em1)==2L)

}
\keyword{ util }