How can i use Discrete wavelet transform (DWT) on a matrix

I have data set of 327 subjects i have read all the dataset in one variable that is T1. T1 size is 1 x 327 and each cell has 19200 x 14. i want to read each data and perform dwt on each one data i.e 19200x 1 and i want it in a loop ( like 1 to 14). I want 2 - level dwt and db4 and extract detail and approximation in matrix

Can someone please help me i have done several methods but didn't get the answer

%% READING THE DATA 
% Task1
myFolder = 'D:\Finall Sorted data\Task 1';
% Get a list of all files in the folder with the desired file name pattern.
filePattern = fullfile(myFolder, '*.csv');
theFiles = dir(filePattern);
n = length(theFiles);
for k = 1 : n
    baseFileName = theFiles(k).name;
    T1{k} = readmatrix(fullfile(theFiles(k).folder, baseFileName));  
end 
S = []; 
P = 0; 
sz = 0; % Size of matrix
for i = 1 : 327 
    
    S{i} = T1{1,i}; % to read the data
    
    for j = 1 : 14
        
        P = S(1:19200:j);
        sz = size(P); 
        % dwt method       
    end
end

[AH]

Hi Sameer,

• There is a typo in the code P = S(1:19200:j) where j = 1:14. Perhaps, you meant P = S(1:19200,j);.
• Did you try wavedec2?

[Sameer Ingale]

Yes, but didn’t get the answer

[Walter Roberson]

    S{i} = T1{1,i}; % to read the data
    

Why are you doing that? You are copying from a cell array to a cell array.

   P = S(1:19200:j);

S is a cell array, not a numeric array. The result of the () indexing is going to be a cell array.

dwt2() cannot process a cell array.

[Sameer Ingale]

I want the size of data within S.

so what should i use to instead of cell array to process ?

[Walter Roberson]

    for j = 1 : 14
        
        P = S(1:19200:j);

Suppose j were 1. Then you would have S(1:19200:1) . But the end value is the same as the initial value, so that will be just S(1) . The same is true for all the other values of j from 1 to 14. j would have to be at lest 19201 for 1:19200:j to include more than one element.

Where you for some reason interested in 1:j:19200 ? That is, the first time [1, 2, 3, 4, ...] and the second time [1, 3, 5, 7, ...] and the third time [1 4 7 10, ...] and so on? Or were you interested in S(1:19200,j) ?

size(1:19200,j) is going to be 19200 x 1 unless j is non-scalar (or is the logical value false)

If you want to know about the size of the data in T1 then you would be more likely to use

    S = T1{1,i};

Answer 1

[Nayan]

Hi

As I understand you want to perfrom discrete wavelet transform on a matrix. This can be performed using dwt2(X,wname).

For futher querry you can share the Data and the exact description of problem that you are facing.

Happy to help!