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.

Examples

Run this code

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))

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