R: Compute and return weaving permutation for conversion from...

getarrvec {wavethresh} | R Documentation

## Compute and return weaving permutation for conversion from wst objects to wd class objects.

### Description

Computes weaving permutation for conversion from `wst` objects to `wd`

### Usage

    getarrvec(nlevels, sort=TRUE)

### Arguments

`nlevels` | The `number of levels` in the non-decimated transform for which the permutation is to be computed.
`sort` | If `TRUE` then compute permutation for indexing a `wst` object. If `FALSE` then compute permutation for indexing a `wd` object.

### Details

Conversion of `wst` objects into `wd` objects and vice versa can be carried out using the `convert.wst` and `convert.wd` functions. These latter functions depend on this getarrvec function to compute the permutation which maps coefficients from one ordering to the other.

This function returns a matrix which gives the necessary permutations for scale levels 1 to `nlevels-1`. If you want to get the permutation for the level 0 coefficients of the `wst` object you will have to call the `levarr` function directly.

This permutation is described in Nason, Sapatinas and Sawczenko, 1998.

The function that actually computes the permutations is `levarr`. This function just combines the results from `levarr`.

### Value

A matrix with `nlevel`s-1 columns. Column 1 corresponds to scale level `nlevels-1` in the `wst` object, and column `nlevels-1` corresponds to scale level 1 in the `wst` object. Replace `wst` by `wd` if `sort=FALSE`.

### RELEASE

Version 3.6 Copyright Guy Nason 1997

### Author(s)

G P Nason

### See Also

`convert`, `convert.wd`, `convert.wst`, `levarr`, `wst`, `wst.object`, `wpst`.

### Examples

    #
    # What would the permutation be for a wst
    # object with 4 levels?
    #
    arrvec <- getarrvec(4)
    #arrvec
    #      [,1] [,2] [,3]
    # [1,]    1    1    1
    # [2,]    9    9    9
    # [3,]    2    5    5
    # [4,]   10   13   13
    # [5,]    3    2    3
    # [6,]   11   10   11
    # [7,]    4    6    7
    # [8,]   12   14   15
    # [9,]    5    3    2
    #[10,]   13   11   10
    #[11,]    6    7    6
    #[12,]   14   15   14
    #[13,]    7    4    4
    #[14,]   15   12   12
    #[15,]    8    8    8
    #[16,]   16   16   16
    #
    # The permutation for level 3 is in column 1
    # The permutation for level 2 is in column 2
    # The permutation for level 1 is in column 3.
    #
    # The following shows that the above is the right permutation (for level 2
    # at least.
    #
    # Start off with some random normal data!
    #
    myrand <- rnorm(1:16)
    #
    # Now take both the time ordered non-decimated wavelet
    # transform and the packet ordered non-decimated wavelet
    # transform.
    #
    myrwdS <- wd(myrand, type="station")
    myrwst <- wst(myrand)
    #
    # Let's look at the level 2 coefficients of myrwdS
    #
    accessD(myrwdS, level=2)
    # [1] -0.73280829 -0.97892279  1.33305777  1.46320165 -0.94790098
    # [6] -1.39276215  0.40023757  0.82517249 -0.56317955 -0.89408713
    #[11]  0.77166463  1.56204870 -0.34342230 -1.64133182  0.08235115
    #[16]  1.05668106
    #
    # Let's look at the level 2 coefficients of myrwst
    #
    accessD(myrwst, level=2)
    # [1] -0.73280829 -0.94790098 -0.56317955 -0.34342230  1.33305777
    # [6]  0.40023757  0.77166463  0.08235115 -0.97892279 -1.39276215
    #[11] -0.89408713 -1.64133182  1.46320165  0.82517249  1.56204870
    #[16]  1.05668106
    #
    # O.k. So the coefficients are the same, but they are not in the
    # same order as in myrwdS. So let's use the permutation in the
    # second column of arrvec to reorder the myrwst coefficients
    # to have the same order as the myrwdS ones
    #
    accessD(myrwst, level=2)[arrvec[,2]]
    # [1] -0.73280829 -0.97892279  1.33305777  1.46320165 -0.94790098
    # [6] -1.39276215  0.40023757  0.82517249 -0.56317955 -0.89408713
    #[11]  0.77166463  1.56204870 -0.34342230 -1.64133182  0.08235115
    #[16]  1.05668106
    #
    # These coefficients have the correct ordering.

[Package wavethresh version 4.6.8 Index]