accessD: Get wavelet expansion coefficients from wavelet structure.
Description
The coefficients from a wavelet expansion in a wavelet decomposition structure
(returned from wd or wr) are packed into a single vector in that structure.
This function extracts the coefficients
corresponding to a particular resolution level.
Usage
accessD(wd.obj, level, boundary=FALSE)
Arguments
wd.obj
Wavelet decomposition structure from which you wish to extract the
expansion coefficients.
level
The level that you wish to extract. If the "original" data has
2^m data points then there are m possible levels that you could want
to access, indexed by 0,1,...
Value
A vector of the extracted coefficients.
item
boundary
Details
The wd (wr) function produces a wavelet decomposition (reconstruction)
structure.
The need for this function is a consequence of the pyramidal structure
of Mallat's algorithm and the memory efficiency gain achieved by
storing the pyramid as a linear vector. AccessD obtains information about
where the coefficients appear from the fl.dbase component of
wd.obj, in particular the array fl.dbase$first.last.d which
gives a complete specification of index numbers and offsets for
wd.obj$D.
Note that this function and accessC only work on objects of class
wd. Also, you have to use putD to put wavelet coefficients into a
wd object.
example(wd)
## Get the 3rd level coefficients of a decompositionaccessD(wds, level=3)
## Do a qqnorm plot to assess the normality of some coefficientsqqnorm(accessD(wds, level=8))