wpcoef

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]);
subplot(2,1,1)
plot(x)
title('Signal')
axis tight
subplot(2,1,2)
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 woman2
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)
title('Packet (1,0) Coefficients')
colormap(pink)

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