R: Get Smoothed Data from Wavelet Structure

accessC.mwd {wavethresh} | R Documentation

## Get Smoothed Data from Wavelet Structure

### Description

The smoothed and original data from a multiple wavelet decomposition structure, `mwd.object` ect (e.g. returned from `mwd`) are packed into a single matrix in that structure. TRUE his function extracts the data corresponding to a particular resolution level.

### Usage

    ## S3 method for class 'mwd'
    accessC(mwd, level = nlevelsWT(mwd), ...)

### Arguments

`mwd` | Multiple wavelet decomposition structure from which you wish to extract the smoothed or original data if the structure is from a wavelet decomposition, or the reconstructed data if the structure is from a wavelet reconstruction.
`level` | The level that you wish to extract. By default, this is the level with most detail (in the case of structures from a decomposition this is the original data, in the case of structures from a reconstruction this is the top-level reconstruction).
`...` | any other arguments

### Details

The mwd function produces a wavelet decomposition structure.

For decomposition, the top level contains the original data, and subsequent lower levels contain the successively smoothed data. So if there are `mwd$filter$npsi*2^m` original data points (`mwd$filter$npsi` is the multiplicity of wavelets), there will be `m+1` levels indexed 0,1,...,m. So

`accessC.mwd(Mwd, level=m)`

pulls out the original data, as does

`accessC.mwd(mwd)`

To get hold of lower levels just specify the level that you're interested in, e.g.

`accessC.mwd(mwd, level=2)`

Gets hold of the second level.

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 matrix of coefficients. AccessC obtains information about where the smoothed data appears from the fl.dbase component of mwd, in particular the array `fl.dbase$first.last.c` which gives a complete specification of index numbers and offsets for `mwd$C`.

Note also that this function only gets information from mwd class objects. To put coefficients into mwd structures you have to use the putC.mwd function.

See Downie and Silverman, 1998.

### Value

A matrix with `mwd$filter$npsi` rows containing the extracted data of all the coefficients at that level.

### RELEASE

Version 3.9.6 (Although Copyright Tim Downie 1995-6.)

### Author(s)

G P Nason

### See Also

`accessD.mwd`, `draw.mwd`, `mfirst.last`, `mfilter.select`, `mwd`, `mwd.object`, `mwr`, `plot.mwd`, `print.mwd`, `putC.mwd`, `putD.mwd`, `summary.mwd`, `threshold.mwd`, `wd`

### Examples

    #
    # Get the 3rd level of smoothed data from a decomposition
    #
    dat <- rnorm(32)
    accessC.mwd(mwd(dat), level=3)

[Package wavethresh version 4.6.8 Index]