[Eeglablist] pop_spectopo jagged spectrum

[Maximilien Chaumon]

Thanks Makoto, I investigated the issue a bit and found out that it was indeed because i didn't high pass filter the data prior to calling pop_spectopo. If I do, the spectrum looks fine. (I thought i replied to all but did only to Andreas.)




Best,

Max

On Wed, Sep 2, 2015 at 7:48 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
wrote:

> Dear Maximilien,
> I completely agree with Andreas. Your data must have a signal with very
> high amplitude. Use 'trimOutlier' plugin to find where it happens in your
> data (in both time domain and channels)
> http://sccn.ucsd.edu/wiki/Plugin_list_process
> 'File' -> 'Manage EEGLAB extensions' and find trimOutlier.
> Makoto
> On Fri, Aug 28, 2015 at 12:28 AM, Andreas Widmann <widmann at uni-leipzig.de>
> wrote:
>> Hi Max,
>>
>> pwelch is quite sensitive to stronger DC offsets. I have seen similar
>> patterns before. Do you possibly analyze raw Biosemi data? Could you please
>> try to highpass filter the data?
>>
>> Best,
>> Andreas
>>
>> > Am 27.08.2015 um 12:22 schrieb Maximilien Chaumon <
>> maximilien.chaumon at gmail.com>:
>> >
>> > Hi,
>> >
>> > Running a spectopo command on a continuous dataset as follows:
>> > spec = pop_spectopo(EEG,1,[],'EEG','noplot','on','percent',5);
>> > I get a terrible jagged spectrum, really ugly like a saw.
>> > I tried to get to the bottom of the problem and ended up looking at the
>> point where this pwelch function from signal toolbox is called. The
>> spectrum that comes out of it is messed up (similar to above).
>> > So I made sure this pwelch function isn't used and it shows a much nicer
>> (normal) power spectrum.
>> >
>> > Anyone had this issue already? How did you solve it?
>> >
>> > I filed a bug: Bug 1791
>> >
>> >
>> > Max
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> -- 
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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