I am using the queue counter, I have put the queue counter in VISSIM GUI and saved & enabled it but while i am coding it in MATLAB the results are showing NaN, Why is it so

%Link Numbers

Link_Num_1=Link_i.ItemByKey(5);

Link_Num_2=Link_i.ItemByKey(7);

Link_Num_3=Link_i.ItemByKey(13);

Link_Num_4=Link_i.ItemByKey(23);

simulation_duration = 7200; % Total simulation time in seconds

interval = 1; % Collect queue length every 120 seconds

num_intervals = simulation_duration / interval; % Number of 120-second intervals (60)

% Initialize matrix for queue lengths (60 rows)

queue_lengths = zeros(num_intervals, 1);

% Get queue counter

queue_counters_1 = Link_Num_1.QueueCounters.GetAll;

qc1 = queue_counters_1{1}; % First queue counter

% Display queue counter info

disp(['Number of queue counters: ', num2str(length(queue_counters_1))]);

disp(['Queue Counter Object: ', class(qc1)]);

disp(['Queue Counter Name: ', qc1.get('AttValue', 'Name')]);

% Run simulation and collect queue length every 120 seconds

interval_idx = 0; % Counter for interval index

for t = 1:interval:simulation_duration

% Run simulation for 120 seconds

for step = 1:interval

sim.RunSingleStep;

end

% Increment interval index

interval_idx = interval_idx + 1;

% Get queue length

queue_length = qc1.get('AttValue', 'QLen(Current, Last)');

if isnan(queue_length)

queue_length = 0; % Replace NaN with 0

end

queue_lengths(interval_idx, 1) = queue_length;

% Display queue length for this interval

disp(['Time ', num2str(t), 's: Queue Length = ', num2str(queue_length)]);

end

disp('Queue Length collection complete.');

Answer 1

[Kautuk Raj]

I suspect you are getting NaN because the queue counter might not be properly set up or accessed. Could you try these quick fixes?

1. Run a step before reading: Add sim.RunSingleStep; before the loop to initialize the simulation.
2. Check if queue counter exists: Make sure queue_counters_1 is not empty.
3. Use correct attribute: Try 'QLen(Current)' instead of 'QLen(Current, Last)'.
4. Ensure it is placed correctly: In VISSIM, confirm the queue counter is on the right link/lane and enabled.

I hope one of the above troubleshooting steps will help resolve the issue.