Error using ilwt Expected LEVEL to be a scalar with value <= 1.

[ca,cd] = lwt(x1,'LiftingScheme',lsc,'Level',2,'Int2Int',true);

...working on ca

x11 = ilwt(double(CA),  cd, 'LiftingScheme',lsc,'Int2Int',true,'Level',2);

Error using ilwt

Expected LEVEL to be a scalar with value <= 1.

Error in ilwt>ilwtParser (line 339)

validateattributes(level, {'numeric'},...

Error in ilwt (line 82)

[LS,ext,level,~,isI2I] = ilwtParser(lvl,varargin{:});

Answer 1

[Umeshraja]

Hi @Baydaa,

It seems you're encountering an error while using the 'ilwt' function for the Inverse Lifting Wavelet Transform. The issue arises because the 'Level' argument in the 'ilwt’ function must be a non-negative integer less than or equal to length(cd) - 1 where ‘cd’ is the ‘Detail coefficients’. length of ‘cd’ is Lx1 where ‘L’ is the ‘Level’ mentioned in 'lwt' function.

Below is a demonstration of how to perform these arguments correctly

% Define the input data
x1 = 1:100;

% Create a lifting scheme using the 'db3' wavelet
lsc = liftingScheme('Wavelet', 'db3');

% Perform the Lifting Wavelet Transform on the data
% 'Level' is set to 5
[ca, cd] = lwt(x1, 'LiftingScheme', lsc, 'Level', 5, 'Int2Int', true);

% Display the length of the detail coefficients (cd)
disp(['Length of cd: ', num2str(length(cd))]);

Length of cd: 5

% Perform the Inverse Lifting Wavelet Transform (ILWT)
% 'Level' is set to 4, which must be <= length(cd) - 1
x11 = ilwt(double(ca), cd, 'LiftingScheme', lsc, 'Int2Int', true, 'Level', 4);

% Display the reconstructed data
disp('Reconstructed data using ILWT:');

Reconstructed data using ILWT:

disp(x11');

     2     4     6     8    11    12     6

For more information on the ‘lwt’ and ‘ilwt’ functions, please refer to these MATLAB R2021b documentation links:

• lwt: https://www.mathworks.com/help/releases/R2021b/wavelet/ref/lwt.html
• ilwt: https://www.mathworks.com/help/releases/R2021b/wavelet/ref/ilwt.html

Hope it resolves your issue!

[Ludovico]

Hello, I apologize for the intrusion.

I am encountering the following issue: when I perform signal reconstruction in a non-integer scenario , i.e. with 'Int2Int' removed and set to true (I correctly configure the reconstruction coefficients such that the 'Level' is set to 4, which must be ≤ length(cd) − 1)), however, after the reconstruction, the resulting signal does not match the original. In particular, it appears “compressed,” as though it were scaled on the left by a factor less than 1. What could be causing this incorrect reconstruction?

Thanks in advance