\name{buildQMatrix}
\alias{buildQMatrix}
\title{Builds a Q-matrix from an Assessment Model Description.}
\description{
This builds a Q Matrix from the output of getEMParametersForAMD
or getLMParametersForAMD.
}
\usage{buildQMatrix(plist)
}

\arguments{
  \item{plist}{A collection of parameter objects created from parsing an
    Assessment Model Description.}
}
\value{
  A data frame whose rows correspond to observable outcome variables and
  whose columns contain key parameters.  The first three columns give
  the name of the Evidence Model, Task (for Link Models) and
  observable.  The next column give the task difficulty.  Then follow a
  number of column corresponding to the proficiency variables.  The
  entries in this column are the log of the slope parameter (if the
  proficiency is relevant for the obserevable) or zero (if not).
  Finally, a number of columns for the Difficulty Increment parameters
  are provided.
}
\details{
  This function is the second part of building a Q-Matrix from an
  Assessment Model Description file.  It takes the output of the
  \code{getEMParametersForAMD} or \code{getLMParametersForAMD} which is
  a list of parameter vector objects organized by model, and creates a
  Q-Matrix.  Note that the entries in the Q-Matrix are the log slope
  parameters, and irrelevant proficiency variables are indicated by NAs.

  Note that only DiBello--Samejima family parameters are included in the
  Q-Matrix, hyper-Dirichlet type parameters are filtered out.
}
\author{Russell Almond}
\note{Hyperdirichlet distributions are given NA values for corresponding
row.}
\seealso{
  \code{\link{getEMParametersForAMD}},\code{\link{getLMParametersForAMD}},
  \code{\link{buildVMatrix}}
}
\examples{
# Assumes StatShop is installed on Test Machine
StatShop <- Sys.getenv("STATSHOP")
if (StatShop == "") {
  warn("StatShop not installed, skipping test.")
} else {
fc <- paste(StatShop,"TestScripts","ICT","Version0","Hybrid","FixedContext",
      sep=.Platform$file.sep)

## This command finds the name of the AMD files in the current
## directory.  Rest of the script assumes that the first one is the
## one you want to use.
amds <- list.files(fc,"amd.xml$")
amdfile <- paste(fc,amds[1],sep=.Platform$file.sep)

## This version of the command works with Assessment Model Description 
## files (from Portal), it looks at evidence models.
allemp <- getEMParametersForAMD(amdfile)

### This command builds the Q-Matrix
QM <- buildQMatrix(allemp)

### This command writes it out.
\dontrun{
write.table(QM,"QMatrix.csv",sep=",",eol="\r\n")
}

}
}
\keyword{interface}