www.gusucode.com > wavelet 源码程序 matlab案例代码 > wavelet/CriticallySampledWaveletPacketAnalysisExample.m
%% Critically Sampled Wavelet Packet Analysis % This example shows how to obtain the wavelet packet transform of a 1-D % signal. The example also demonstrates that frequency ordering is different % from Paley ordering. %% % Create a signal consisting of a sine wave with a frequency of $7\pi/8$ % radians/sample in additive white Gaussian N(0,1/4) noise. The sine wave % occurs between samples 128 and 512 of the signal. rng default; dwtmode('per'); n = 0:1023; indices = (n>127 & n<=512); x = cos(7*pi/8*n).*indices+0.5*randn(size(n)); %% % Obtain the wavelet packet transform down to level 2 using the Daubechies % least asymmetric wavelet with 4 vanishing moments. Plot the wavelet packet % tree. T = wpdec(x,2,'sym4'); plot(T); %% % Find the Paley and frequency ordering of the terminal nodes. [tn_pal,tn_freq] = otnodes(T); %% % |tn_freq| contains the vector |[3 4 6 5]|, which shows that the highest % frequency interval, $[3\pi/4,\pi)$, is actually node 5 in the Paley-ordered % wavelet packet tree. %% % Click on node (2,2) in the wavelet packet tree to see that the frequency % ordering correctly predicts the presence of the sine wave. % % <<../wptree1.png>> %% % The wavelet packet transform of a 2-D image yields a quarternary wavelet % packet tree. Load an example image. Use the biorthogonal B-spline wavelet % with 3 vanishing moments in the reconstruction wavelet and 5 vanishing % moments in the decomposition wavelet. Plot the resulting quartenary wavelet % packet tree. load tartan; T = wpdec2(X,2,'bior3.5'); plot(T);