[Eeglablist] Problem with epoching and boundary events

Andreas Widmann widmann at uni-leipzig.de
Tue Jan 14 01:13:03 PST 2014


If this is fixed now, you can also close duplicate bug 1518 where I already had reported the same problem last year.
https://sccn.ucsd.edu/bugzilla/show_bug.cgi?id=1518

Thanks! Best,
Andreas

Am 13.01.2014 um 20:08 schrieb James Desjardins <jdesjardins at brocku.ca>:

> Hi Phillipp,
> 
> I have posted your issue to EEGLAB Bugzilla (bug# 1552) and committed the fix to the EEGLAB SVN repository (revision 10261).
> 
> Let me know if my replication of your account captures the issue that you described (taken from the bugzilla report):
> 
> I replicated the problem by creating three events in a continuous dataset
> containing a boundary discontinuity at 4.2 seconds into the recording. I added
> event type 's3' (three seconds into the recording), event type 's4' (four
> seconds into the recording) and event type 's5' (five seconds into the
> recording).
> 
> If I epoch the data (+/- .5 seconds) to only 's4' I appropriately get "no epochs" related
> errors.
> 
> If I epoch to {'s3' 's4'} I get 2 epochs and the boundary event is missing from
> the data discontinuity in the second epoch.
> 
> If I epoch to {'s3' 's4' 's5'} I get 3 epochs and the boundary event is missing
> from the data discontinuity in the second epoch.
> 
> If I add a boundary discontinuity at time 5.2 seconds into the recording and
> then epoch to {'s3' 's4' 's5'} I get 2 epochs, one for 's3' and the second for
> 's5'. In this case again the boundary event is missing from the data
> discontinuity in the second epoch (for 's5'), but it appropriately dropped the
> 's4' discontinuous epoch.
> 
> The issue of the final boundary event in the segmented dataset being dropped
> can be traced back to line 505 in the current eeg_checkset function where it is
> removing the final boundary event if its latency is greater than the size of
> the second dimension of EEG.data. This step only seems to be appropriate when
> the data are continuous (EEG.trials=1).
> 
> 
> Thanks for noticing and reporting this!
> 
> 
> James Desjardins, MA
> Electrophysiology Technologist
> Cognitive and Affective Neuroscience Lab, Psychology Department
> Jack and Nora Walker Centre for Lifespan Development Research
> Brock University
> 500 Glenridge Ave.
> St. Catharines, ON, Canada L2S 3A1
> 905-688-5550 x4676
> --
> "'Cause you never can tell What goes on down below!
> "This pool might be bigger Than you or I know!"
> 
> McElligot's Pool
> Dr.Seuss 1947
> 
> ________________________________________
> From: eeglablist-bounces at sccn.ucsd.edu [eeglablist-bounces at sccn.ucsd.edu] on behalf of Philipp Spachtholz [Spachtholz at psy.lmu.de]
> Sent: January-10-14 6:20 AM
> To: eeglablist at sccn.ucsd.edu
> Subject: [Eeglablist] Problem with epoching and boundary events
> 
> Dear all,
> 
> i am new to EEGLAB and started doing some scripting and came across a
> problem. Maybe
> someone can help me.
> 
> I import data from Brain Vision Analyzer (where i marked bad data
> stretches). I then read out the
> datapoints of these bad strechtes using the event "userdefined" and
> subject those values to
> eeg_eegrej. This seems to work well and the bad stretches are replaced
> with a boundary event.
> 
> However when I do epoching over all stimulus events (each stimulus event
> only occurs once in my experiment), some of them are epoched although
> the interval contains a boundary event.
> For example i have a Stimulus type 'S 79' which is followed by a
> boundary event within 1 second. If i specifically select this event for
> epoching with a time range of [-0.6 1.8] i get an error (which makes
> sense to me).
> If i select stimulus type 'S 79' and the succeding event after the
> boundary event (or another one), only the event
> after the boundary is selected for epoching --> I get 1 epoch.
> 
> However when i select more than 2 stimulus types for epoching, e.g. 3
> events then I get 3 epochs,
> including the S 79.
> 
> Do you have any idea why this might happen?
> This happens both using the script and the gui.
> 
> thank you very much for your help
> 
> Philipp Spachtholz
> 
> 
> --
> Dipl. Psych. Philipp Spachtholz
> 
> Department of Psychology
> University of Munich
> Leopoldstrasse 13
> 80802 Germany
> Phone: +49 (89) 2180-5229
> E-Mail: Spachtholz at psy.lmu.de
> 
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