\name{nlatent}
\alias{nlatent}
\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{
nlatent(pm)
}
\arguments{
  \item{pm}{
    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{
pm1 <-
  TimelessNormalPM(muMean=c(Mechanics=2,Fluency=2),  varWeight=3,
                   precScale=solve(matrix(c(.7,.3,.3,.7),2,2)), Sdf=3)

stopifnot(nlatent(pm1)==2L)

}
\keyword{ util }