wpcoef

R2026b

Wavelet packet coefficients

Syntax

x = wpcoef(wpt,n)

x = wpcoef(wpt)

Description

wpcoef is a one- or two-dimensional wavelet packet analysis function.

x = wpcoef(wpt,n) returns the coefficients associated with the node n of the wavelet packet tree wpt. If node n does not exist, x = [].

x = wpcoef(wpt) is equivalent to x = wpcoef(wpt,0).

Examples

Obtain Wavelet Packet Coefficients

Load a 1-D signal. Save the current extension mode.

load noisdopp
x = noisdopp;
origMode = dwtmode("status","nodisp");

Use dwtmode to change the extension mode to zero-padding. Obtain the wavelet packet tree object corresponding to the 3-level wavelet packet decomposition of the signal using the db1 wavelet. Plot the tree.

dwtmode("zpd","nodisp")
wpt = wpdec(x,3,"db1");
plot(wpt)

Obtain the coefficients at the node (3,0). Plot the signal and coefficients.

cfs = wpcoef(wpt,[3 0]);
tiledlayout(2,1)
nexttile
plot(x)
title("Signal")
axis tight
nexttile
plot(cfs)
title("Packet (3,0) Coefficients")
axis tight

Load an image. Obtain the wavelet packet tree that corresponds to a one-level wavelet packet decomposition of the image using the sym4 wavelet.

load mask
t = wpdec2(X,1,"sym4");

Plot the tree.

plot(t)

Obtain the coefficients at the node (1,0). Plot the coefficients.

cfs = wpcoef(t,[1 0]);
figure
imagesc(cfs)
colormap(pink)
title("Packet (1,0) Coefficients")

Restore the extension mode to the original setting.

dwtmode(origMode,"nodisp")

Input Arguments

wpt — Wavelet packet tree

wptree object

Wavelet packet tree, specified as a wptree object.

n — Node

0 (default) | nonnegative integer | 1-by-2 vector

Node in a wavelet packet tree, specified as a nonnegative integer, or pair of nonnegative integers. See depo2ind and ind2depo.

Example: If wpt = wpdec(1:256,2,"sym4"), then wpcoef(wpt,3) and wpcoef(wpt,[2 0]) specify the same node.

Data Types: double

Output Arguments

x — Node coefficients

vector | matrix

Node coefficients, returned as a vector or matrix.

Data Types: double

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

The wpcoef function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced before R2006a

R2026b: Use thread-based environments

You can use wpcoef in thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.