\Header{sortedXyData}{Create a sortedXyData object}
\methalias{sortedXyData.default}{sortedXyData}
\keyword{manip}{sortedXyData}
\begin{Description}\relax
This is a constructor function for the class of \code{sortedXyData}
objects.  These objects are mostly used in the \code{initial}
function for a self-starting nonlinear regression model, which will be
of the \code{selfStart} class.\end{Description}
\begin{Usage}
\begin{verbatim}
sortedXyData(x, y, data)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] a numeric vector or an expression that will evaluate in
\code{data} to a numeric vector 
\item[\code{y}] a numeric vector or an expression that will evaluate in
\code{data} to a numeric vector 
\item[\code{data}] an optional data frame in which to evaluate expressions
for \code{x} and \code{y}, if they are given as expressions 
\end{ldescription}
\end{Arguments}
\begin{Value}
A \code{sortedXyData} object. This is a data frame with exactly
two numeric columns, named \code{x} and \code{y}.  The rows are
sorted so the \code{x} column is in increasing order.  Duplicate
\code{x} values are eliminated by averaging the corresponding \code{y}
values.\end{Value}
\begin{Author}\relax
Jose Pinheiro and Douglas Bates\end{Author}
\begin{SeeAlso}\relax
\code{\Link{selfStart}}, \code{\Link{NLSstClosestX}},
\code{\Link{NLSstLfAsymptote}}, \code{\Link{NLSstRtAsymptote}}\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
library( nls )
data( DNase )
DNase.2 <- DNase[ DNase$Run == "2", ]
sortedXyData( expression(log(conc)), expression(density), DNase.2 )
\end{ExampleCode}
\end{Examples}

