accessD.mwd {wavethresh} | R Documentation

## Get wavelet coefficients from multiple wavelet structure (mwd).

### Description

The wavelet coefficients from a multiple wavelet decomposition structure, `mwd.object`, (e.g. returned from `mwd`) are packed into a single matrix in that structure. This function extracts the coefficients corresponding to a particular resolution level.

### Usage

    accessD.mwd(mwd, level, ...)

### Arguments

`mwd` | Multiple 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 `mwd$filter$npsi*2^m` data points (`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)
`...` | any other arguments

### Details

The `mwd` function produces a `multiple wavelet decomposition object` .

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. AccessD obtains information about where the coefficients appear from the fl.dbase component of `mwd`, in particular the array `fl.dbase$first.last.d` which gives a complete specification of index numbers and offsets for `mwd$D`.

Note that this function and `accessC` only work on objects of class `mwd` to extract coefficients. You have to use `putD.mwd` to insert wavelet coefficients into a `mwd` object.

See Downie and Silverman, 1998.

### Value

A matrix with `mwd$filter$npsi` rows containing the extracted coefficients.

### RELEASE

Tim Downie 1995-6

### See Also

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

### Examples

    #
    # Get the 3rd level of smoothed data from a decomposition
    #
    data(ipd)
    accessD.mwd(mwd(ipd), level=3)

[Package wavethresh version 4.0-2 Index]