catching a value while matlab is running

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Dimitrios
Dimitrios 2014-10-21
编辑： per isakson 2014-10-22
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
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per isakson
per isakson 2014-10-22
"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
Dimitrios 2014-10-22
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

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回答（2 个）

Robert Cumming
Robert Cumming 2014-10-22
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.
per isakson
per isakson 2014-10-22
编辑：per isakson 2014-10-22
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
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

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