[Eeglablist] ERSP outputs

[Johnson, John T.]

In my experience (much less than Makoto, et al.), the parameters you provide are treated as requests. The time and frequency ranges actually used are based on your data. Things such as the sampling rate can affect the number of frequencies generated. Time can be altered by the filtering method used (Hanning, etc.), number of cycles specified, etc. If I were troubleshooting this, I would set a breakpoint in std_ersp.m at line 347 which is the call to newtimef(). The newtimef() call actually does the work of calculating the time-frequency information. From there, you can inspect the variables being passed to newtimef() and see if window size, multi-taper, etc. are affecting your results. If this doesn’t provide answers, you might need to dig into newtimef.m itself to see how the parameters are modified before the calculations are performed. E.g. set a breakpoint at 878 and inspect the parameters in the g struct.

Regards,
John

On 16 Jul 2019, at 15:44, Erika Nyhus wrote:

Hi Makoto,


I am confused because when I run std_precomp it says the output frequencies are 3-125 Hz, 100 frequencies and the time range is -240-1440, 200 timepoints, but when I look at the ersp data after plotting the output frequencies are from 3-49 Hz, 75 frequencies and the time range is -100-1440, 183 timepoints.


Erika Nyhus, Ph.D.
Department of Psychology and Program in Neuroscience

6900 College Station
Bowdoin College
Brunswick, ME 04011
________________________________
From: Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
Sent: Friday, July 12, 2019 11:57:55 PM
To: Erika Nyhus
Cc: EEGLAB List
Subject: Re: ERSP outputs

Dear Erika,

Basic facts about the parameters can be found here.
https://sccn.ucsd.edu/mediawiki/images/a/a6/C2_A3_Time-frequencyDecAndAdvancedICAPracticum_updateJan2017.pdf<https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsccn.ucsd.edu%2Fmediawiki%2Fimages%2Fa%2Fa6%2FC2_A3_Time-frequencyDecAndAdvancedICAPracticum_updateJan2017.pdf&data=02%7C01%7Cenyhus%40bowdoin.edu%7Cb8d6248ec2074b17355908d707466229%7C984e32e5f98a4600aa3227c3f948abe3%7C1%7C1%7C636985871232653522&sdata=aqeS9fx60AYuJ0445EnbfuYOYSTjdOH9QS5YDYapCjY%3D&reserved=0>

However, 'nfreqs', 100 generated 75 frequencies does not make sense. Are you sure 'nfreqs' was properly recognized when you performed the calculation? I have never heard of it.

Makoto

On Thu, Jul 11, 2019 at 11:04 AM Erika Nyhus <enyhus at bowdoin.edu<mailto:enyhus at bowdoin.edu>> wrote:

I am confused about the outputs for ERSPs in std_precomp. My data was epoch from -800-2000 ms and the only inputs I set for erspparams was 'cycles' [3 .8], 'nfreqs' 100, 'ntimesout' 200. I am not sure why the output frequencies are from 3-49 Hz, 75 frequencies and why the time range is -100-1440, 183 timepoints.


Erika Nyhus, Ph.D.
Department of Psychology and Program in Neuroscience

6900 College Station
Bowdoin College
Brunswick, ME 04011


--
Makoto Miyakoshi
Assistant Project Scientist, Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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John T. Johnson
PhD Candidate - Cognitive Motor Control Laboratory
Lab TA NEURO 2001 Principles
School of Biological Sciences
Georgia Institute of Technology

678-575-2093
john.johnson at gatech.edu<mailto:john.johnson at gatech.edu>