How can I extract the frequencies of details and approximation of a signal that decomposed by "wavedec" command?

%% This commands used for extracting details and approximations ;

%% I want to Know haw can I earn frequencies of each detail and approximation????

clc

clear

close all

a=signal;

Fs=5e6;

dt=1/Fs;

wname='db10';

nLevel=4;

[C, L]=wavedec(a,nLevel,wname);

A4 = appcoef(C,L,'db10',4);

[D1,D2,D3,D4] = detcoef(C,L,[1,2,3,4]);

Answer 1

[Suraj Kumar]

Hi Esmail,

1. To extract the frequencies of details and approximation of a signal that was decomposed by ‘wavedec’ command, you can define the wavelet decomposition parameters and perform the decomposition of the signal into detailed coefficients.

wname = 'db10';     
nLevel = 4;        
[C, L] = wavedec(a, nLevel, wname); 
A4 = appcoef(C, L, wname, 4); 
[D1, D2, D3, D4] = detcoef(C, L, [1, 2, 3, 4]); 

2.Then you can determine the frequency ranges for each detail and approximation level based on the Nyquist frequency and decomposition level.

for i = 1:nLevel 
    f_high = Fs / (2^(i-1)); % Upper frequency of the detail 
    f_low = Fs / (2^i);      % Lower frequency of the detail 
    fprintf('Detail D%d: %.2f Hz to %.2f Hz\n', i, f_low, f_high); 
end 
f_approx = Fs / (2^nLevel); 
fprintf('Approximation A%d: 0 Hz to %.2f Hz\n', nLevel, f_approx); 

You can refer to the output below for better understanding:

To know more about ‘wavedec’, ‘appcoef’ or ‘detcoef’ functions in MATLAB, you can refer the following documentations:

• https://www.mathworks.com/help/wavelet/ref/wavedec.html
• https://www.mathworks.com/help/wavelet/ref/appcoef.html
• https://www.mathworks.com/help/wavelet/ref/detcoef.html

Hope this works for you!