\HeaderA{accessD.mwd}{Get wavelet coefficients from multiple wavelet structure (mwd).}{accessD.mwd}
\keyword{manip}{accessD.mwd}
\begin{Description}\relax
The wavelet coefficients from a multiple wavelet decomposition structure, \code{\LinkA{mwd.object}{mwd.object}}, (e.g. returned from \code{\LinkA{mwd}{mwd}}) are packed into a single matrix in that structure. This function extracts the coefficients corresponding to a particular resolution level.
\end{Description}
\begin{Usage}
\begin{verbatim}
accessD.mwd(mwd, level, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{mwd}] Multiple wavelet decomposition structure from which you wish to extract the expansion coefficients.
\item[\code{level}] The level that you wish to extract. If the "original" data has \code{mwd\$filter\$npsi*2\textasciicircum{}m} data points (\code{mwd\$filter\$npsi} being the multiplicity of the multiple wavelets) then there are m possible levels that you could want to access, indexed by 0,1,...,(m-1) 
\item[\code{...}] any other arguments
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
The \code{\LinkA{mwd}{mwd}} function produces a \code{multiple wavelet decomposition object} .

The need for this function is a consequence of the pyramidal structure of \code{Mallat's algorithm} and the memory efficiency gain achieved by storing the pyramid as a linear matrix. AccessD obtains information about where the coefficients appear from the fl.dbase component of \code{\LinkA{mwd}{mwd}}, in particular the array \code{fl.dbase\$first.last.d} which gives a complete specification of index numbers and offsets for \code{mwd\$D}. 

Note that this function and \code{\LinkA{accessC}{accessC}} only work on objects of class \code{\LinkA{mwd}{mwd}} to \emph{extract} coefficients. You have to use \code{\LinkA{putD.mwd}{putD.mwd}} to insert wavelet coefficients into a \code{\LinkA{mwd}{mwd}} object. 

See Downie and Silverman, 1998.
\end{Details}
\begin{Value}
A matrix with \code{mwd\$filter\$npsi} rows containing the extracted coefficients.
\end{Value}
\begin{Section}{RELEASE}
Tim Downie 1995-6
\end{Section}
\begin{SeeAlso}\relax
\code{\LinkA{accessD.mwd}{accessD.mwd}}, \code{\LinkA{draw.mwd}{draw.mwd}}, \code{\LinkA{mfirst.last}{mfirst.last}}, \code{\LinkA{mfilter.select}{mfilter.select}}, \code{\LinkA{mwd}{mwd}}, \code{\LinkA{mwd.object}{mwd.object}}, \code{\LinkA{plot.mwd}{plot.mwd}}, \code{\LinkA{print.mwd}{print.mwd}}, \code{\LinkA{putC.mwd}{putC.mwd}}, \code{\LinkA{putD.mwd}{putD.mwd}}, \code{\LinkA{summary.mwd}{summary.mwd}}, \code{\LinkA{threshold.mwd}{threshold.mwd}}, \code{\LinkA{wd}{wd}}, \code{\LinkA{wr.mwd}{wr.mwd}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
#
# Get the 3rd level of smoothed data from a decomposition
#
data(ipd)
accessD.mwd(mwd(ipd), level=3)
\end{ExampleCode}
\end{Examples}

