# [Eeglablist] Maximum segment average amplitude, from single epochs

Gaspar Lukacs lkcsgaspar at gmail.com
Tue Mar 25 02:02:41 PDT 2014

```Bastien: Considering your first question I realised that my description was
not right, sorry. I can't get around what I actually need: first I should
get sample ERPs (of different events) by bootstrapping, and only then I
should use the algorithm I described, to compute mean amplitude differences
(between events), to eventually get the distribution of those differences -
as in, for example,
http://groups.psych.northwestern.edu/rosenfeld/documents/CTPPsychophysiology2008.pdf(pp.
908-909), and on second thought I probably better contact the authors,
as this procedure seems quite specific.

Still, thank you very much for your answer Makoto, those commands might
prove useful.

On 25 March 2014 04:42, Bastien Boutonnet <bastien.b1 at gmail.com> wrote:

> Actually, because I implemented something like that once, but didn't use
> squeeze what would the added value of squeeze be? I looked into the doc of
> that function but I'm not sure I understand what it does.
>
> Makoto, do you have a better way of explaining it than the matlab doc on
> squeeze()?
>
> -
> Bastien Boutonnet, Ph. D.
> Department of Psychology
> University of Wisconsin, Madison
> bastienboutonnet.com
>
>
> On 24 March 2014 20:12, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>
>> Dear Gaspar,
>>
>> Without checking it with Matlab...
>> To make it simple, I'll use millisecond instead of datapoints.
>>
>> channelOfInterest = 10; % let's say you want to see Ch10.
>> maxPoint = squeeze(max(EEG.data(channelOfInterest,300:800,:),[],2));
>> minPoint =
>> squeeze(max(EEG.data(channelOfInterest,maxPoint:1300,:),[],2)); % Does this
>> work? If not (and probably not), use for simple for loop, like
>>
>> minPoint = zeros(1,length(maxPoint));
>> for n = 1:length(maxPoint)
>> minPoint(n) =
>> squeeze(max(EEG.data(channelOfInterest,maxPoint(n):1300,:),[],2));
>> end
>>
>> meanMaxValue =
>> squeeze(mean(EEG.data(channelOfInterest,maxPoint-50:maxPoint+50,:),2));
>> meanMinValue =
>> squeeze(mean(EEG.data(channelOfInterest,maxPoint-50:minPoint+50,:),2));
>>
>> Let me know if this does not work.
>>
>> Makoto
>>
>>
>>
>> 2014-03-24 10:21 GMT-07:00 Bastien Boutonnet <bastien.b1 at gmail.com>:
>>
>> Do you basically want to collect the maxima and then average over those
>>> maximums?
>>>
>>> -
>>> Bastien Boutonnet, Ph. D.
>>> Department of Psychology
>>> University of Wisconsin, Madison
>>> bastienboutonnet.com
>>>
>>>
>>> On 24 March 2014 05:44, Gaspar Lukacs <lkcsgaspar at gmail.com> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I have problems with data extraction from single epochs, for which I'll
>>>> probably need an algorithm. Specifically, within each epoch, from 300 to
>>>> 800 ms I need to get the maximum positive 100 ms segment average amplitude,
>>>> and then from the midpoint of this segment to 1300 ms, the maximum negative
>>>> 100 ms segment average.
>>>>
>>>> The closest thing I could find is a "meanepoch.m" script which gets
>>>> mean values between given latencies from single epochs - but it cannot
>>>> search for maximum mean values (i.e. segment  averages)..
>>>>
>>>> I would be very grateful for any suggestions.
>>>>
>>>> Regards,
>>>> Gaspar
>>>>
>>>> /Institute of Psychology, University of Szeged/
>>>>
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>>>
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>>
>>
>>
>> --
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
>>
>
>
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