\Header{loess.control}{Set Parameters for Loess}
\keyword{smooth}{loess.control}
\begin{Description}\relax
Set control parameters for \code{loess} fits.\end{Description}
\begin{Usage}
\begin{verbatim}
loess.control(surface = c("interpolate", "direct"),
              statistics = c("approximate", "exact"),
              trace.hat = c("exact", "approximate"),
              cell = 0.2, iterations = 4, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{surface}] should be fitted surface be computed exactly or via
interpolation from a kd tree?
\item[\code{statistics}] should the statistics be computed exactly or
approximately? Exact computation can be very slow.
\item[\code{trace.hat}] should the trace of the smoother matrix be computed
exactly or approximately. It is recommended to use the approximation
for more than about 1000 data points.
\item[\code{cell}] if interpolation is used this controls the accuracy of the
approximation via the maximum number of points in a  cell in the kd
tree. Cells with more than \code{floor(n*span*cell)} points are subdivided.
\item[\code{iterations}] the number of iterations used in robust fitting.
\end{ldescription}
\end{Arguments}
\begin{Value}
A list with components
\begin{ldescription}
\item[\code{surface}] 
\item[\code{statistics}] 
\item[\code{trace.hat}] 
\item[\code{cell}] 
\item[\code{iterations}] 
\end{ldescription}
\end{Value}
\begin{Author}\relax
B.D. Ripley\end{Author}
\begin{SeeAlso}\relax
\code{\Link{loess}}\end{SeeAlso}

