catching a value while matlab is running

I am building a simulation with many functions using OOP(beginner). Sometimes I have some values from different variables that are not desirable but I can not see them while the simulation is running. So I was wondering if there is any way to catch this value while the simulation is running. I believe it could be done inside the functions but there so many that its inefficient and time-consuming to do it. Can addlisterer be used for that or any other way? Any suggestions?

Thanks in advance

[José-Luis]

Whatever you do, overheads are inevitable. What have you tried so far?

[Dimitrios]

I didn't start to implement something for this task. When I wrote for time consuming I was meaning not computational time but the time to implement that. I am saying that cause there are more than 100 functions and the variables that I want to check are more than one, so trying to write in every function is not so attractive. I was thinking something with addlistener but I have zero experience of using it and I am not even sure if it could be used.

[José-Luis]

I can't see a way around looking at all the events you are interested in, unless they are somehow related.

I can't help you with the specifics of OOP (I am biased against its use in Matlab) or addListener() since I have never used it. Just a quick look at the documentation tells me that you can pass the function you want to listen to as an argument, which can be used to simplify your code.

[per isakson]

"some values from different variables" &nbsp Are the names of the variables known? Same name in many functions?

"Can addlisterer be used for that or any other way?" &nbsp Yes, but that requires you to add notify(handle), Notify listeners that event is occurring in 100 methods.

[Dimitrios]

Thanks for the reply.The names of the variables are known.Same name in many functions.I ll try to use addlistener for first time then.(btw I cant find any video tutorial for that,only the example with the bank from the documentation.Anything else out there?) :p

Answer 1

[Robert Cumming]

you could use listeners, but you could also use the dbstop ability to stop on condition, i.e.

dbstop in MFILE at LINENO if 'EXPRESSION'

where Expression is of the format:

myVariable > 1000

You can also add these conditionss interactively in the editor by right clicking on the line number and adding a Conditional Breakpoint.

By adding these conditions your code will stop if the condition is true and you can debug from there.

Answer 2

[per isakson]

The documentation on Events and Listeners is okay and I didn't find any examples with banks. However, I had to run and modify the examples to really get it. See

• Learning to Use Events and Listeners
• Listen for Changes to Property Values

I doubt that Events and Listeners is a good approach (to spy om a simulation). It takes some extra code to use Events and Listeners to peek on a running simulation. You will have to either make all the properties (variables) Observable or litter the code with notify. And I guess the performance will be hurt.

You need to make some serious experiments before you start adding code to 100 methods.

&nbsp

An alternative approach builds on the answer by Robert Cumming: &nbsp dbstop if error .... &nbsp I have a hammer and see a nail in your question :)

Building blocks

• enable_spying.m &nbsp is a script, which contains statements like: &nbsp dbstop in mfile at lineno if my_spy( variables_of_interest ). &nbsp It will be hundreds similar statements.
• my_spy &nbsp always returns false. It shall not interrupt the simulation.
• my_spy &nbsp could cause all sorts of side effects, which is the trick: &nbsp make test on the input arguments; add point to a diagram; call a logger (e.g. log4m); etc.
• log4m - A powerful and simple logger for matlab, by Luke Winslow (and there a few more loggers in the File Exchange)
• ALWAYSONTOPby Elmar Tarajan to keep the diagram visible
• tracer4m excels in the use of side effects of &nbsp dbstop in mfile at lineno if foo

Use

• run the script, enable_spying.m
• start your simulation
• watch the output file of log4m with an editor. I use notepad++

Pro

• not a single line of extra code in your simulation program
• simple to switch on and off the spying feature
• does not affect the performance when switched off

Con

• non-standard. However, it is based on documented features of Matlab.
• the script, enable_spying.m, must be edited to reflect changes in the code of the simulation program
• and more - I guess