Error using horzcat Dimensions of arrays.

Hi,

Can anyone please help me to solve this error? Thanks!

clc;
% Load the video
video = VideoReader('test1.mp4');

% Initialize the background model
background = read(video, 1);
for i = 2:video.NumberOfFrames
    frame = read(video, i);
    background = imlincomb(0.5, background, 0.5, frame);
end

% Initialize variables to store the vehicle count and position
vehicle_count = 0;
vehicle_positions = [];

% Loop through each frame in the video
for i = 1:video.NumberOfFrames
    frame = read(video, i);
    
    % Subtract the background
    difference = abs(frame - background);
    difference = imbinarize(rgb2gray(difference), 0.1);
    
    % Remove small objects
    difference = bwareaopen(difference, 500);
    
    % Find connected components
    components = bwconncomp(difference);
    
    % Loop through each connected component
    for j = 1:components.NumObjects
        % Get the pixels of the current component
        pixels = components.PixelIdxList{j};
        
        % Calculate the bounding box of the component
        [rows, cols] = ind2sub(components.ImageSize, pixels);
        bbox = [min(cols), min(rows), max(cols) - min(cols), max(rows) - min(rows)];
        
        % Check if the component is a vehicle
        if bbox(3) * bbox(4) > 50000
            % Increment the vehicle count
            vehicle_count = vehicle_count + 1;
            
            % Store the position of the vehicle
            vehicle_positions = [vehicle_positions; bbox(1) + bbox(3) / 2, bbox(2) + bbox(4) / 2];
        end
    end
end

% Display the results
disp(['Number of vehicles: ', num2str(vehicle_count)]);
disp(['Vehicle positions: ', num2str(vehicle_positions)]);

The error is:

Error using horzcat
Dimensions of arrays being concatenated are not consistent.

Error in traffic_count (line 52)
disp(['Vehicle positions: ', num2str(vehicle_positions)]);

Answer 1

[Jan]

num2str(x) replies a CHAR matrix, if x contains several rows:

a = num2str(rand(2))

a = 2×19 char array
    '0.32683     0.52028'
    '0.29436    0.023409'

You cannot concatenate a CHAR vector and a CHAR matrix horizontally. Maybe you want:

disp('Vehicle positions:');
for k = 1:height(vehicle_positions)
    fprintf('%g ', vehicle_positions(k, :));
    fprintf('\n');
end

or:

disp(['Vehicle positions: ', mat2str(vehicle_positions)]);