accessD {wavethresh}R Documentation

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,...{},(m-1).
boundary If this argument is TRUE then all of the boundary correction values will be returned as well (note: the length of the returned vector may not be a power of 2). If boundary is false, then just the coefficients will be returned. If the decomposition (or reconstruction) was done using periodic boundary handling then this option has no effect.

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.

Value

A vector of the extracted coefficients.

See Also

wr and wd for background information; accessC, filter.select, threshold, putC, putD.

Examples

example(wd)

## Get the 3rd level coefficients of a decomposition
accessD(wds, level=3)

## Do a qqnorm plot to assess the normality of some coefficients
qqnorm(accessD(wds, level=8))

[Package wavethresh version 2.2-9 Index]