MATLAB Answers


How can read data of entity in queue

Asked by ozcan
on 12 Dec 2012

Hi, please somebody help me I need to attribute values of entity which are waiting on queue at the any t time. How can read this data of entity when entity wait in queue ?

  1 Comment

Ryan G
on 14 Dec 2012

What are you trying to accomplish? You can pull the attribute off the entity before it enters the queue for later use, or perhaps use a different block to accomplish your task.

2 Answers

Answer by Ryan G
on 17 Dec 2012
Edited by Ryan G
on 17 Dec 2012
 Accepted answer

You can try using Decdatt's suggestion along with persistent variables in the MATLAB function block.

I would create a feedback loop with an Attribute Function block (MATLAB function block for SimEvents) and an Output switch to push blocks from the queue. One output from the Output switch would connect to a path combiner to create the loop. You can have a timer attribute attached to the entity to determine when to push that entity from the queue or you can update the position of the entities when one leaves the queue.

Furthermore, you can use assignin to push data from the Attribute Function workspace to the base workspace. Using all these tools you should be able to recreate any of the queues available in the library, however, they will probably not be as efficient and it will cost you in simulation speed.

  1 Comment

on 19 Dec 2012

thanks Ryan this solution is very helpful,

Answer by Devdatt Lad
on 14 Dec 2012

Currently you cannot peek inside a queue to look at entity attributes. As RyanG said, you can only pull out attribute values as entities enter or leave the queue.

With that in mind, you can put together some blocks that will cause all entities in the queue to leave the queue, and be fed back to the same queue in a feedback loop. Use a signal to open a gate or something that triggers this whole feedback loop. As each entity goes round the loop, pull off any attribute values you care about and send the entity back into the same queue.

This scheme will work if you want to iterate over ALL entities in the queue. If you just want the attribute value of the last entity that entered, or last entity to leave the queue, Ryan's suggestion would be better. Use a Signal Latch to save the attribute value before the entity enters the queue.

  1 Comment

on 17 Dec 2012

yes your approach is very logical but I want to send to matlab this informations. Do you know any matlab function-code that read this data. Already my model has embeded matlab functions block and I can use this code in this block.

Join the 15-year community celebration.

Play games and win prizes!

Learn more
Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

MATLAB Academy

New to MATLAB?

Learn MATLAB today!