# No Subject

**URL:** <https://psychtoolbox.discourse.group/t/no-subject/683>\
**Category:** Uncategorized\
**Created:** [February 23, 2006, 11:22am UTC](https://psychtoolbox.discourse.group/t/no-subject/683 "2006-02-23T11:22:22Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\
**Post date:** [February 23, 2006, 11:22am UTC](https://psychtoolbox.discourse.group/t/no-subject/683/1 "2006-02-23T11:22:22Z")

</div>

Hi all,  
  
I am a newbie to the psychtoolbox. I have met with the following  
difficulties/questions:  
  
a) Does it support debugging in Matlab on PC? I have set breakpoints and  
found breakpoints were erased by psychtoolbox and basically they have no  
effects.   
  
b) During Psychphysics experiments, I have switched back to Matlab  
command line to check output results, but then how to switch back to  
Psychtoolbox Screen? I was never able to switch back, every time I ended up  
with kill the Matlab session.  
  
c) In the Quest functions, do they have a valid range for “tTest”,  
which is a variable in the QuestDemo? I have tried to manually set the tTest  
to be -10, because my experiment needs half of the time 10^tTest = 0, (I am  
using tTest as in log-scale, so for real value to drive the intensity of my  
stimuli, I use 10^tTest. Half of the time I want to set my intensity to be  
0, so I manually set tTest to be -10, or -100, etc. However, QuestUpdate  
does not allow out-of-range values; it always generate the following error  
message:  
  
??? Function 'strcmp' is not defined for values of class 'struct'.  
  
Error in ==\> strcmp at 24  
  
 [varargout{1:nargout}] = builtin('strcmp', varargin{:});  
  
Error in ==\> QuestUpdate at 34  
 if  
strcmp(oldWarning,'backtrace')  
  
Error in ==\> FindPsychmetricThreshold at 133  
  
 q=QuestUpdate(q,tTest,response);  
  
I want to debug, but Matlab on PC with Psychtoolbox does not allow me to  
debug…  
  
Could you please help me out?  
  
Thanks a lot for your help!  
Boquan.