replace sub-matrix values with zeros

Hello, I have a large matrix C, which contains a number of matrices in the format C{i}{j}(k1,k2). The size of the matrix (value of k1 and k2) are different for different i and j values. I would like to set all k1 and k2 values to zero except for a certain i and j values. For example, i=1:7, and j varies from 1 to 128 for different i values. I want to keep the values of i=1, and j=1 and replace all other values to zero. e.g. C{1,1}{1,1}. Please help me to make the loop where i can keep the original size of the matrix but replace the values with zero except the target ones. Related information: I encountered this problem when I am using curvelet. I decomposed the image into different scales and wedges. Now I want to do an inverse curvelet transform of the original image without a particular scale and wedge. I would like to separate and visualize the variations at different scales and wedges. I wonder how I can make the matrix right. thanks a lot in advance. please help

Answer 1

[BhaTTa]

To achieve this, you need to loop through all elements of the cell array C and set the values to zero for all indices except for the specified ones (i=1 and j=1). You want to retain the original sizes of the matrices but replace their values with zeros.

Here's a MATLAB script to do this:

% Example setup: create a sample cell array C with nested cell arrays
C = cell(3, 3);
for i = 1:3
    for j = 1:3
        C{i, j} = cell(1, 3);
        for k = 1:3
            C{i, j}{k} = rand(i + 1, j + 1); % Random matrices of different sizes
        end
    end
end

% Display original C
disp('Original C:');
disp(C);

% Apply the zeroing operation
for i = 1:size(C, 1)
    for j = 1:size(C, 2)
        % Skip the specified indices (i=1 and j=1)
        if ~(i == 1 && j == 1)
            % Loop through each nested cell array
            for k = 1:length(C{i, j})
                % Get the size of the current matrix
                [k1, k2] = size(C{i, j}{k});
                % Set all elements to zero
                C{i, j}{k} = zeros(k1, k2);
            end
        end
    end
end

% Display modified C
disp('Modified C:');
disp(C);