waht does the command "cfs = read(wpt,'data') " return?

wpt is the wavelet packet tree. does "cfs = read(wpt,'data') " return the sum of the coefficients of the tree nodes at the bottom level？

But the result is in fact different from the original signal?

Why?

thanks

Answer 1

[Wayne King]

Hi,

cfs = read(wpt,'data');

returns the coefficients in the terminal nodes of the wavelet packet tree. These are not equal to the data.

For example:

dwtmode('per');
x = randn(16,1);
T = wpdec(x,3,'db2');
plot(T)

Now, click on (3,0) (3,1), (3,2) and so on.

You see in each one of these nodes, there are 4 coefficients. Since there are 8 such nodes, there are a total of 32 coefficients.

cfs = read(T,'data');

returns these 32 coefficients.

[Dingguo Lu]

Wayne King

thanks for your help!

[Dingguo Lu]

Wayne,

I have further questions.

1. With your example, the size of "cfs" is 1x16. Why? I am little confused.

2. Are the coefficients in "cfs" ordered by the order of (3,0) (3,1), (3,2) and so on?

3. Is there any way that I can reconstruct original signal from the terminal nodes?

4. Do the terminal nodes carry same frequency and magnitude information as the original signal?

Might two many questions. Still, these are really important for me.

Thanks,