Converting .mat to .txt which also contains cell arrays.

I am using the Lidar labeler app from the lidar toolbox in MATLAB. When i annotate the pcds and save them, they are saved in .mat files. We know, when there is more than 1 object in a frame, they are stored in cell arrays. I have 9 classes in my annotation and i want to store these label data frame wise and class wise in a text file. How do i do it? For your reference, the structure of the Label data is attached.

I have tried accessing the cell arrays but failed continuously. Would really appreciate your help in this regard.

Thank you in advance!

[Ayush Modi]

If you can provide the data, it would be easier to help you.

Also, could you elaborate what do you mean by labeling the data in a text file? Would you like to create separate text files for each annotation?

[Rik]

Do you want something like JSON perhaps?

[Lab]

I would like to create seperate text files for each annotation, yes.

A JSON file is also something i want to work with soon.

[Rik]

What does jsonencode do with this data?

Answer 1

[prabhat kumar sharma]

Hi Lab,

I understand that you are facing issue with storing data label wise and class wise in a text file.

To store the label data frame-wise and class-wise from the Lidar Labeler app in MATLAB, you can extract the relevant information from the saved MAT files and write it to a text file. Here's a step-by-step approach to help you accomplish this:

1. Load the label data from the .mat file:

load('label_data.mat'); % Replace 'label_data.mat' with the path to your label data file

2. Access the necessary fields in the label data structure:

frameData = label_data.frameAnnotations;

3. Iterate through each frame and extract the class-wise labels:

numFrames = numel(frameData);  
numClasses = numel(label_data.labelDefinitions);
% Create a cell array to store the labels for each frame and class
labels = cell(numFrames, numClasses);
for i = 1:numFrames
    for j = 1:numClasses
        % Extract the labels for each class in the current frame
        labels{i, j} = frameData(i).objectAnnotations(j).classification;
    end
end

4. Write the label data to a text file:

filename = 'label_data.txt'; % Specify the filename for the text file
fid = fopen(filename, 'w'); % Open the file for writing
for i = 1:numFrames
    fprintf(fid, 'Frame %d:\n', i);
    for j = 1:numClasses
        fprintf(fid, 'Class %d: ', j);
        % Write the labels for each class in the current frame
        if isempty(labels{i, j})
            fprintf(fid, 'No label\n');
        else
            fprintf(fid, '%s\n', labels{i, j});
        end
    end
    fprintf(fid, '\n');
end
fclose(fid); % Close the file

You can use the above code for reference for your MAT file and class and frame label.

After executing the above code, you will have a text file (`label_data.txt`) containing the label data frame-wise and class-wise. Each frame will be labelled with the corresponding class information. If there is no label for a specific class in a frame, it will be indicated as "No label" in the text file.

I hope it helps!