A Trous wavelet decomposition

Dear all friends,

I am very new with Matlab. I am currently working on a flow forecasting project. I have a set of water flow data. My professor ask me to do A Trous decomposition for 10 levels. Therefore I use the following Matlab code:

function dwt = FWT_ATrou(x,L);
% FWT_ATrou -- Fast Dyadic Wavelet Transform (periodized, orthogonal)
% Usage
% dwt = FWT_ATrou(x,L)
% Inputs
% x 1-d signal; length(x) = 2^J = n
% L Coarsest Level of V_0; L << J
% Outputs
% dwt an n times J-L+1 matrix
% giving the wavelet transform of x at all dyadic scales.
% Description
% To reconstruct use IWT_ATrou
% See Also
% IWT_ATrou, MakeATrouFilter
[lodyadf,dlodyadf,hidyadf,dhidyadf] = MakeATrouFilter('Spline',3);

[n,J] = dyadlength(x) ;
D = J-L;
dwt = zeros(n,D+1);
x = ShapeAsRow(x);
dwt(:,1) = x';
for d = 1:D,
s = dwt(:,1)';
s2 = s;
for j = 1:2^(d-1)
s2 = lshift(s2);
dwt(:,d+1) = iconv(hidyadf,s)';
for j = 1:2^(d)
p = lshift(dwt(:,d+1)');
dwt(:,d+1) = p';
dwt(:,1) = iconv(lodyadf,s2)';

f = zeros(1,2*length(lodyadf));
f(1:2:2*length(lodyadf)-1) = lodyadf;

f2 = zeros(1,2*length(hidyadf));
f2(1:2:2*length(hidyadf)-1) = hidyadf;

lodyadf = f;
hidyadf = f2;

I have set up my data as X, then I just randomly put a number for L. I am start getting confuse here. Can anyone give me some advices to move forward ? Please.


  • Hai, I am also working on a similar problem using A trous wavelet algorithm. Put the size of X to be 2^N and L shpuld be less than N. I think you are using wavelab for this purpose. You should also have an eye on the boundary treatment if you are dealing with non-stationary data.

    my email id is maheswaran15@gmail.com If you want you can contact me for further details

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