[Eeglablist] Plotting ERSP with Merged Channels

[Makoto Miyakoshi]

Dear Julie,

> Specifically, I have a 80 (freqs) x 200 (time points) x 1 (channel: three
averaged into one) x 16 (subjects) array for each condition.

At least you want to apply Matlab function squeeze() to drop that singleton
dimension.

> Any advice on methods you know are supported by eeglab that allows you to
plot ERSP changes with multiple channels averaged into a single plot would
be greatly appreciated!

I don't think there is dedicated EEGLAB function to visualize ERSP. It uses
standard function such as imagesc() etc.

> I see this commonly done in the literature but am uncertain of how it is
executed.

Looks like you are familiar with coding. Why don't you plot it yourself?
It's quite easy. It's like this. Assuming that you have your 80x200x16 data
in 'data' and epoch time in EEG.times,

figure
imagesc(EEG.times, mean(data,3)); axis xy

Makoto



On Thu, Oct 27, 2016 at 8:39 PM, Schneider, Julie <jxs114631 at utdallas.edu>
wrote:

> Hi Makoto,
>
> Thank you so much for your timely response. Yes, I would like to average
> together these channels. I've successfully done this; however, that leaves
> my data in a 4-D array that I am struggling to plot. Specifically, I have a
> 80 (freqs) x 200 (time points) x 1 (channel: three averaged into one) x 16
> (subjects) array for each condition.
>
> Any advice on methods you know are supported by eeglab that allows you to
> plot ERSP changes with multiple channels averaged into a single plot would
> be greatly appreciated! I see this commonly done in the literature but am
> uncertain of how it is executed.
>
> Thanks again for your assistance!
> Julie
>
>
>
> On Oct 27, 2016, at 9:33 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>
> Dear Julie,
>
> > I would like to investigate significant differences between my two
> conditions of interest when FC1,FC2, and C2 are merged together
>
> Merged? Do you mean averaged? If so, do you want to do it after computing
> ERSP, or do you want to concatenate the three time series?
>
> Anyway, I have never heard of concatenating channels in that way is
> supported by the current EEGLAB. You may be able to average ERSP of FC1,
> FC2, and C2, but you still need to write code to do it.
>
> Makoto
>
>
>
> On Thu, Oct 27, 2016 at 9:38 AM, Schneider, Julie <jxs114631 at utdallas.edu>
> wrote:
>
>> Greetings,
>>
>>
>> Using the EEGlab toolbox, I have created a study and can plot the ERSP
>> for an individual electrode, but cannot plot the average of multiple
>> channels. Specifically, I would like to investigate significant differences
>> between my two conditions of interest when FC1,FC2, and C2 are merged
>> together. In attempting to solve this problem, I found a previous inquiry
>> on the eeglab listserv:
>>
>> https://sccn.ucsd.edu/pipermail/eeglablist/2011/004188.html.
>>
>>
>> I have successfully been able to follow a portion of Arno's response ["*erspdata
>> may then contain data of size (5 elecs x 12 subjects) for example when
>> plotting scalp topographies. **You may then average the first dimension*"];
>> however, I have not been able to successfully " *replot the result"*.
>> The clear issue being that the new variable created by averaging this
>> dimension [which is actually the third dimension in my data, and is
>> executed using M=mean(my cell array, 3)] can not be plotted using
>> std_erspplot because it is not a variable within the study. Other methods
>> of plotting, such as image, imagesec, ft_plot_topo, and various attempts
>> through the Fieldtrip toolbox, have proven unsuccessful.
>>
>>
>> Any additional information on how I may plot these merged channel files
>> would be greatly appreciated. Further, the eeglablist question to which I
>> am referencing was posted circa 2011, and I would imagine there may be
>> newer methods/plug-ins that allow for this analysis to be conducted. Any
>> recommendations that follow another methodology are welcomed and
>> appreciated!
>>
>>
>> Best Regards,
>>
>> Julie
>>
>>
>> Julie M. Schneider, M.S.
>>
>> Doctoral Student
>>
>> The Developmental Neurolinguistics Lab
>>
>> Brain and Behavioral Sciences, University of Texas at Dallas
>>
>>
>>
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>
>
>
> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
>


-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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