Field reference for multiple structure elements that is followed by more reference blocks is an error. and undefined function histogram

Field reference for multiple structure elements that is followed by more reference blocks is an error.

Error in (line 71)

scatter([vehicles.position(:,1)], [vehicles.position(:,2)], 'filled', 'MarkerFaceColor', 'b');

Undefined function 'histogram' for input arguments of type 'double'.

Error in (line 176)

histogram(vehicleProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'b',

'EdgeColor', 'w');

clear;
clc;
close all;

% Parameters
numVehicles = 50;          % Number of vehicles
numEdges = 3;              % Number of edge computing nodes
numClusters = 5;           % Number of clusters in the Things layer
cloudCapacity = 1000;      % Cloud computing capacity
edgeCapacity = [100, 150, 200]; % Edge computing capacity
taskRate = 0.1;            % Task generation rate per vehicle (tasks/second)
communicationDelayEdge = 1;% Communication delay for edge offloading (seconds)
communicationDelayCloud = 5;% Communication delay for cloud offloading (seconds)
distanceThreshold = 100;   % Maximum distance for edge offloading (meters)
clusterRadius = 200;       % Radius for clustering in the Things layer (meters)
vehicleComputingPower = 50;% Computing power of each vehicle (arbitrary units)

% Initialize vehicles
vehicles = struct('position', num2cell(rand(numVehicles, 2)*1000, 2), 'tasks', [], 'ip', '', 'computingPower', vehicleComputingPower);

% Initialize edge nodes
edges = struct('position', num2cell(rand(numEdges, 2)*1000, 2), 'tasks', [], 'capacity', edgeCapacity, 'ip', '');

% Cloud initialization
cloud = struct('tasks', [], 'capacity', cloudCapacity, 'ip', '8.8.8.8');

% Initialize clusters in the Things layer
clusters = struct('center', num2cell(rand(numClusters, 2)*1000, 2), 'members', []);

% Form clusters in the Things layer
for i = 1:numVehicles
    minDist = inf;
    nearestCluster = 0;
    for j = 1:numClusters
        dist = norm(vehicles(i).position - clusters(j).center);
        if dist < minDist
            minDist = dist;
            nearestCluster = j;
        end
    end
    clusters(nearestCluster).members = [clusters(nearestCluster).members, i];
end

% Assign IP addresses for vehicles in each cluster
for i = 1:numClusters
    clusterSize = length(clusters(i).members);
    clusterIPRange = 10 * (i - 1) + (1:clusterSize);
    for j = 1:clusterSize
        vehicles(clusters(i).members(j)).ip = ['192.168.', num2str(i), '.', num2str(clusterIPRange(j))];
    end
end

% Initialize arrays to store processing times
vehicleProcessingTime = [];
edgeProcessingTime = [];
cloudProcessingTime = [];

% Simulation loop
figure;
for t = 1:100
    % Generate tasks for vehicles
    for i = 1:numVehicles
        if rand < taskRate
            vehicles(i).tasks = [vehicles(i).tasks; t];
        end
    end
    
    clf; % Clear figure for each time step
    
    % Plot vehicles
    scatter([vehicles.position(:,1)], [vehicles.position(:,2)], 'filled', 'MarkerFaceColor', 'b');
    hold on;
    
    % Plot edge nodes
    scatter([edges.position(:,1)], [edges.position(:,2)], 'filled', 'MarkerFaceColor', 'g');
    
    % Plot cloud
    scatter(cloud.position(1), cloud.position(2), 'filled', 'MarkerFaceColor', 'r');
    
    % Plot clusters
    for i = 1:numClusters
        scatter(clusters(i).center(1), clusters(i).center(2), 'x', 'MarkerEdgeColor', 'k', 'LineWidth', 2);
    end
    
    % Offload tasks from vehicles to either edge nodes or cloud
    for i = 1:numVehicles
        % Determine if edge offloading is possible
        edgeOffload = false;
        for j = 1:numEdges
            if norm(vehicles(i).position - edges(j).position) <= distanceThreshold && ~isempty(edges(j).tasks)
                edgeOffload = true;
                break;
            end
        end
        
        % Offload task to edge node if possible, otherwise to cloud
        if edgeOffload
            for j = 1:numEdges
                if norm(vehicles(i).position - edges(j).position) <= distanceThreshold && ~isempty(edges(j).tasks)
                    task = vehicles(i).tasks(1);
                    vehicles(i).tasks(1) = [];
                    edges(j).tasks = [edges(j).tasks; task];
                    disp(['Task from vehicle ', num2str(i), ' offloaded to edge ', num2str(j)]);
                    break;
                end
            end
        else
            if ~isempty(cloud.tasks)
                task = vehicles(i).tasks(1);
                vehicles(i).tasks(1) = [];
                cloud.tasks = [cloud.tasks; task];
                disp(['Task from vehicle ', num2str(i), ' offloaded to cloud']);
            end
        end
    end
    
    % Process tasks at edge nodes
    for j = 1:numEdges
        if ~isempty(edges(j).tasks)
            completedTasks = edges(j).tasks(edges(j).tasks <= t - communicationDelayEdge);
            edges(j).tasks = setdiff(edges(j).tasks, completedTasks);
            disp(['Edge ', num2str(j), ' processed ', num2str(length(completedTasks)), ' tasks']);
            % Record processing time
            edgeProcessingTime = [edgeProcessingTime, t - completedTasks];
        end
    end
    
    % Process tasks at the cloud
    if ~isempty(cloud.tasks)
        completedTasks = cloud.tasks(cloud.tasks <= t - communicationDelayCloud);
        cloud.tasks = setdiff(cloud.tasks, completedTasks);
        disp(['Cloud processed ', num2str(length(completedTasks)), ' tasks']);
        % Record processing time
        cloudProcessingTime = [cloudProcessingTime, t - completedTasks];
    end
    
    % Process tasks on vehicles (for simplicity, assume immediate processing)
    for i = 1:numVehicles
        if ~isempty(vehicles(i).tasks)
            completedTasks = vehicles(i).tasks(vehicles(i).tasks <= t);
            vehicles(i).tasks = setdiff(vehicles(i).tasks, completedTasks);
            disp(['Vehicle ', num2str(i), ' processed ', num2str(length(completedTasks)), ' tasks']);
            % Record processing time
            vehicleProcessingTime = [vehicleProcessingTime, zeros(1, length(completedTasks))]; % Assuming immediate processing
        end
    end
    % Move vehicles (random movement for visualization)
    for i = 1:numVehicles
        vehicles(i).position = vehicles(i).position + randn(1, 2)*5; % Random movement
    end
    
    % Respond to neighbor requests (for visualization, no actual communication)
    for i = 1:numVehicles
        % Find neighbors of vehicle i
        neighbors = [];
        for j = 1:numVehicles
            if i ~= j && norm(vehicles(i).position - vehicles(j).position) <= distanceThreshold
                neighbors = [neighbors, j];
            end
        end
        
        % Display neighbors
        disp(['Vehicle ', num2str(i), ' has neighbors: ', num2str(neighbors)]);
    end
    hold off;
    axis([0 1000 0 1000]); % Set axis limits
    title(['Time Step: ', num2str(t)]);
    xlabel('X Position');
    ylabel('Y Position');
    grid on;
    pause(0.5); % Pause to visualize each time step
end

% Plot processing time for each processing entity
figure;
histogram(vehicleProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'b', 'EdgeColor', 'w');
hold on;
histogram(edgeProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'g', 'EdgeColor', 'w');
histogram(cloudProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'r', 'EdgeColor', 'w');
hold off;
title('Processing Time Distribution');
xlabel('Processing Time (time steps)');
ylabel('Probability');
legend('Vehicle', 'Edge', 'Cloud');

[Walter Roberson]

which MATLAB version are you using?

[Catherine]

Matlab R2013a

[Stephen23]

"Matlab R2013a"

Check the documentation of your installed MATLAB version and you will find that HISTOGRAM() does not exist. It was first introduced in R2014b.

For an approximate replacement your installed version has the HIST() function, but note that it may have a different syntax and it does not support any name-value input arguments like your code uses.

[Catherine]

i got the following error after changing from histogram to hist

Error using hist (line 45)

Input arguments must be numeric.

Error in (line 187)

hist(vehicleProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'b',

'EdgeColor', 'w');

[Stephen23]

"i got the following error after changing from histogram to hist"

Which is why I already told you that HIST supports no name-value input arguments. If you then call HIST with many name-value input arguments (as your quoted error message clearly shows), what do you expect to happen?

You should read the documentation of every function that you use. And follow it.

Answer 1

[Voss]

Regarding the error:

Field reference for multiple structure elements that is followed by more reference blocks is an error.

Error in (line 71)

scatter([vehicles.position(:,1)], [vehicles.position(:,2)], 'filled', 'MarkerFaceColor', 'b');

vehicles is a 50x1 structure array; the position field of each element of vehicles is a 1x2 numeric array.

You need to concatenate all the vehicles positions together and then take the first or second column, so this:

% Plot vehicles

pos = vertcat(vehicles.position); % vertical concatentation to get a 50x2 array

scatter(pos(:,1), pos(:,2), 'filled', 'MarkerFaceColor', 'b');

instead of this:

% Plot vehicles

scatter([vehicles.position(:,1)], [vehicles.position(:,2)], 'filled', 'MarkerFaceColor', 'b');

Similiarly for edges. You can do the same for clusters, rather than plotting them in a loop.

But for cloud there is no field called "position", so you'll get an error about that here:

% Plot cloud

scatter(cloud.position(1), cloud.position(2), 'filled', 'MarkerFaceColor', 'r');

I'm not sure what you want to plot from cloud.

[Catherine]

After adjusting i still get this error

Undefined function 'histogram' for input arguments of type 'double'.

Error in (line 187)

histogram(vehicleProcessingTime, 'BinWidth', 1, 'Normalization', 'probability', 'FaceColor', 'b',

'EdgeColor', 'w');

[Voss]

As pointed out elsewhere, you can try to use hist instead of histogram, but the syntax is different.

However, I notice that after I run your code, I get vehicleProcessingTime is all zeros, and edgeProcessingTime and cloudProcessingTime are both empty. Is that expected? If not, check on how those three things are calculated.